book of abstracts - cern indico

QM 2011 - XXII InternationalConference onUltrarelativistic

Nucleus-Nucleus CollisionsSunday, May 22, 2011 - Saturday, May 28, 2011

Centre Bonlieu

Book of Abstracts

Contents

Tagging of eta decay products in Bose-Einstein correlations to analyze chiral restoration 1

Equation of state and initial temperature of quark gluon plasma at RHIC . . . . . . . . . 1

The phase diagram in T-mu-Nc space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Soft-quark bremsstrahlung and energy losses . . . . . . . . . . . . . . . . . . . . . . . . 2

On the fluctuation-dissipation theorem for soft fermionic excitations in a hot QCD plasma 2

Next-to-leading order structure function for DIS off a large nucleus . . . . . . . . . . . . 3

Higher harmonic jet tomography as a probe of fluctuating initial condition geometries inA+A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Flow-Driven Conical Correlations in Heavy-Ion Collisions . . . . . . . . . . . . . . . . . 3

The Single Flavor Color Superconductivity in a Magnetic Field. . . . . . . . . . . . . . . 4

The Subleading Term of the Strong Coupling Expansion of the Heavy-Quark Potential . 4

Mach Cone Induced by γ-Triggered Jets in High-Energy Heavy-Ion Collisions . . . . . . 5

The second act of hydro: shocks and sounds from initial perturbations and jets . . . . . . 5

Viscous QCD matter at RHIC and LHC energies. Insights from viscous hydrodynamics +hadron cascade hybrid approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Non-Extensive Approach to High-Energy Collisions . . . . . . . . . . . . . . . . . . . . . 6

Momentum broadening in weakly coupled quark-gluon plasmas . . . . . . . . . . . . . . 7

Radial and elliptic flow in LHC Pb+Pb collisions from viscous hydrodynamics . . . . . . 7

Direct Photons from microscopic+macroscopic hybrid model . . . . . . . . . . . . . . . . 8

Massive QCD antenna radiation in medium . . . . . . . . . . . . . . . . . . . . . . . . . 8

The QGP shear viscosity: elusive goal or just around the corner? . . . . . . . . . . . . . 8

Jet shower evolution in medium and di-jet asymmetry in PbPb collisions at the LHC . . 9

Experimental study of quark and gluon jets in proton-proton and heavy-ion collisions. . 9

iii

Simulations of thermodynamic and kinetic properties of the strongly coupled quark-gluonplasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Direct jet reconstruction in d+Au collisions at PHENIX . . . . . . . . . . . . . . . . . . . 11

Upsilon production at RHIC and LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Non-extensive Statistical Approach to Fragmentation . . . . . . . . . . . . . . . . . . . . 11

Equilibration and Thermalization of Strongly Coupled Field Theories . . . . . . . . . . . 12

Strong Coupled Pion Superfluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Bulk properties of PbPb collisions at the LHC measured by ALICE . . . . . . . . . . . . . 13

Common discussion with 3 speakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Anisotropic flow from ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Flow measurements from the CMS experiment . . . . . . . . . . . . . . . . . . . . . . . . 14

Quenching of single hadron and photon spectra from RHIC to LHC . . . . . . . . . . . . 14

Particle production at large transverse momentum with ALICE . . . . . . . . . . . . . . 14

Monte Carlo tools for jet quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

STAR on reconstructed jets and jet-like correlations . . . . . . . . . . . . . . . . . . . . . 15

Applying the AdS/CFT correspondence to non-abelian plasmas . . . . . . . . . . . . . . 15

PHENIX heavy flavor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Quarkonia measurements by the CMS experiment in pp and PbPb collisions . . . . . . . 15

Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Correlations and fluctuations from lattice QCD . . . . . . . . . . . . . . . . . . . . . . . 17

p + A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

New challenges at the low energy frontier . . . . . . . . . . . . . . . . . . . . . . . . . . 17

e + A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

The high energy frontier of A-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Non-conformal holography of light and heavy quark jet quenching at RHIC and LHC . . 17

Jet Modification Via The LPM Effect In Infinite Quark Matter . . . . . . . . . . . . . . . . 18

iv

Measuring parton energy loss at RHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Dynamical magnetic effects and the nonphotonic electron puzzle at RHIC . . . . . . . . 18

Overview of the experimental results by the ALICE Collaboration . . . . . . . . . . . . . 19

Results from lead-lead collisions with the ATLAS Detector at the LHC . . . . . . . . . . 19

Overview of the experimental results by the CMS Collaboration . . . . . . . . . . . . . . 19

PHENIX Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

STAR highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Opening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

LHC accelerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Theory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Heavy-ion collisions and QCD: the big picture . . . . . . . . . . . . . . . . . . . . . . . . 20

Soft physics and hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Jets, high-pT hadrons and prompt photons . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Heavy-quarks and quarkonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Initial conditions, low-x QCD, thermalization . . . . . . . . . . . . . . . . . . . . . . . . 21

QCD phase transition, hydrodynamics, hadronization . . . . . . . . . . . . . . . . . . . . 21

Jets, high-pT hadrons, and prompt photons . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Heavy-quarks and quarkonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Medium induced collinear radiation from soft collinear effective theory (SCET) . . . . . 22

Suppression of the repulsive force in nuclear interactions near the chiral phase transition 22

Equation of state of a strongly-interacting QGP and charmonium suppression . . . . . . 23

First-principles derivation of the jet energy-momentum deposition source term in the QGPand its implications for shockwave formation at RHIC and at the LHC . . . . . . . . 23

Momentum dependence of quarkonium production at RHIC and LHC . . . . . . . . . . . 24

Strong color fields effects and baryon/meson anomaly in p+p and central Pb+Pb collisionsat L H C energies(*). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

An effective theory for jet propagation in dense QCD matter: jet broadening, radiativeenergy loss and LHC phenomenology . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Directed Flow in event-by-event hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . 25

Silicon Tracking for the Compressed Baryonic Matter Experiment at FAIR . . . . . . . . 26

Directed flow and early thermalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

v

What is the surface tension of quark gluon bags? . . . . . . . . . . . . . . . . . . . . . . 27

DENSE COLDMATTER STUDYWITH SPECIAL TRIGGERAT TWA, NUCLOTRON, NICAAND FAIR. Project Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Enhancement of flow anisotropies due to magnetic field in relativistic heavy-ion collisions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Initial state fluctuations at RHIC and LHC: hadronic or partonic origin? . . . . . . . . . 28

Centrality dependence of observables in the core - corona model . . . . . . . . . . . . . 29

The realistic QCD equation of state in relativistic heavy-ion collisions and the early Uni-verse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Role of Finite Size Baryons in QCD Phase Transition and Critical Point . . . . . . . . . . 30

Far-from-equilibrium anisotropic collective flow . . . . . . . . . . . . . . . . . . . . . . . 31

Describing sQGP through the Friedberg-Lee model . . . . . . . . . . . . . . . . . . . . . 31

Measurements of Jets and Jet Quenching in sqrt(s_NN)=2.76 TeV PbPb Collisions with theATLAS Detector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Measurement of elliptic flow in sqrt(s_NN)=2.76 TeV PbPb collisions with the ATLAS de-tector at the LHC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Measurement of charged particle pseudorapidity density in PbPb collisions at sqrt(s_NN)= 2.76 TeV with the ATLAS detector at the LHC . . . . . . . . . . . . . . . . . . . . . 32

Measurements of charged particle spectra in sqrt(s_NN)=2.76 PbPb collisions with the AT-LAS detector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Study of Ultraperipheral processes in sqrt(s_NN)=2.76 Pb+Pb collisions with the ATLASdetector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Measurement of higher-order flow harmonics in sqrt(s_NN)=2.76 TeV Pb+Pb collisionswith the ATLAS detector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Measurements of Jet Production and Jet Fragmentation in sqrt(s_NN) = 2.76 TeV Pb+PbCollisions with the ATLAS detector at the LHC . . . . . . . . . . . . . . . . . . . . . 34

Jet quenching from RHIC to LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Effects of parton radiative processes on Quark-Gluon Plasma thermalization . . . . . . . 35

Some new results on high-energy ”jet stopping” in AdS/CFT . . . . . . . . . . . . . . . . 36

Running coupling corrections to high energy inclusive gluon production . . . . . . . . . 36

Characterizing quark gluon plasma by Heavy Flavors . . . . . . . . . . . . . . . . . . . . 36

Heavy quarkonia in a quark-gluon plasma: coupled evolution and dynamics . . . . . . . 37

Study of the expansion and the phase transition of a quark plasma to an hadron phase withthe NJL model using a new QMD approach. . . . . . . . . . . . . . . . . . . . . . . . 37

vi

QCD thermodynamics at intermediate coupling . . . . . . . . . . . . . . . . . . . . . . . 38

Moments of charge fluctuations, pseudo-critical temperatures and freeze-out in heavy ioncollisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Photon and dilepton production from viscous QGP . . . . . . . . . . . . . . . . . . . . . 39

Hydrodynamical analysis of centrality dependence of charged particle’s multiplicity in√sNN=2.76 TeV Pb+Pb collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Entanglement between deconfinement transition and chiral symmetry restoration . . . . 40

Probing nuclear parton densities and parton energy loss processes through photon + heavy-quark jet production in p-A and A-A collisions . . . . . . . . . . . . . . . . . . . . . . 41

Exotic Matter-Antimatter Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Energy Dependence of the Identified Hadron Elliptic Flow and QCD Phase Structure . . 42

Quarkonium production at the LHC: QCD corrections and new observables . . . . . . . 43

Jets, mach cone, hot spots, ridges, harmonic flow, dihadron and γ-hadron correlations inhigh-energy heavy-ion collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Kadanoff-Baym Approach to Thermalization of Gluonic Matter . . . . . . . . . . . . . . 43

Charged-hadron pseudorapidity distributions in the RDM at LHC energies . . . . . . . . 44

Suppression of high p_T hadrons in PbPb Collisions at LHC . . . . . . . . . . . . . . . . 44

A few new experimental results on particle correlations . . . . . . . . . . . . . . . . . . . 45

V1 flow componet at LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Can we see from jet quenching that quark-gluon plasma becomes more perturbative atLHC than at RHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Dilepton interferometry: a tool to characterize different phases of matter produced inheavyion collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Charged Particle’s elliptic flow in 2+1D viscous hydrodynamics at LHC (√s=2.76 TeV) En-ergy in Pb+Pb collision. and QGP viscosity . . . . . . . . . . . . . . . . . . . . . . . . 47

Enhancement of thermal photon production in event-by-event hydrodynamics . . . . . . 47

Initial conditions - Theory perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Initial state fluctuations and their effect on the flow . . . . . . . . . . . . . . . . . . . . . 48

Pion quenching and tomography from RHIC to LHC in the WHDG model . . . . . . . . 49

High resolution numerical scheme for hydrodynamic analysis of heavy ion collisions andformation of an incoming shock wave induced by reheating . . . . . . . . . . . . . . 49

Bulk viscosity of a pion gas and energy-momentum correlations . . . . . . . . . . . . . . 50

ATLAS flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

vii

Collective flow measurements from the PHENIX Experiment . . . . . . . . . . . . . . . . 50

Common discussion with 4 experimental speakers . . . . . . . . . . . . . . . . . . . . . . 51

Nuclear modification factors from the CMS experiment . . . . . . . . . . . . . . . . . . . 51

Recent R_AA Results from the PHENIX Experiment . . . . . . . . . . . . . . . . . . . . 51


Jet measurements by the CMS experiment in pp and PbPb collisions . . . . . . . . . . . . 51

ATLAS jet measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52


Heavy-flavor production in PbPb collisions at the LHC measured with the ALICE detector 52


Quarkonium measurements at the LHC with the ALICE detector . . . . . . . . . . . . . 53


Hadrochemistry – theory status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

ALICE hadrochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

common discussion with 2 speakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

STAR: results from the beam energy scan program . . . . . . . . . . . . . . . . . . . . . 54

NA49/NA61: SPS results on fluctuations & correlations . . . . . . . . . . . . . . . . . . . 54

Production of identified particles in pp and PbPb collisions at LHC energies with the ALICEdetector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Correlations and fluctuations measured by the CMS experiment in pp and PbPb collisions 55

The low energy frontier of A-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Physics opportunities of future p-A runs . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Physics opportunities of e-A colliders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Physics opportunities of e-A colliders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

The high energy frontier of A-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

eA collisions at the Large Hadron-electron Collider . . . . . . . . . . . . . . . . . . . . . 56

Hadrochemistry – theory status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

ALICE hadrochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

common discussion with 2 speakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Quark production far from equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

viii

The Very High Momentum Particle Identification Detector at ALICE . . . . . . . . . . . 57

Highly-anisotropic and strongly-dissipative hydrodynamics for early stages of relativisticheavy-ion collisions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Fireball fragmentation and rapidity correlations of protons . . . . . . . . . . . . . . . . . 58

Deconfinement and chiral transition in QCD at finite temperature . . . . . . . . . . . . . 59

Jet properties in \it p+p and their possible modification in cold nuclear matter in STAR 59

Cavitation and Thermal Dilepton Production in QGP . . . . . . . . . . . . . . . . . . . . 59

D+ →K- π+ π+ Production in pp collisions at LHC with the ALICE detector . . . . . . . 60

First results from hybrid HKM for top RHIC and LHC energies . . . . . . . . . . . . . . . 60

Non−Photonic Electron and Charged Hadron Azimuthal Correlation in p+p Collisions at√s = 500 GeV in STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Dielectron production in Au+Au collisions at √sNN = 39GeV at STAR . . . . . . . . . 62

QGP viscosity coefficients: from weak to strong coupling . . . . . . . . . . . . . . . . . . 62

Equation of state of strongly interacting matter: spectra for thermal particles and intensitycorrelation of thermal photons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Interference of thermal photons from quark and hadronic phases in relativistic collisionsof heavy nuclei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Two freeze-out analysis of hadron yields and spectra at RHIC . . . . . . . . . . . . . . . 64

Measurements of Non-photonic Electron Spectra and Elliptic Flow in Au+Au Collisionsfrom STAR at RHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Effects of final state interactions on charge separation in relativistic heavy ion collisions 65

Nucleon mass generated from confinement and a dynamic generation of the quark masses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Beauty in the QGP from the lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Dimuon radiation at the CERN SPS within a hybrid evolution model . . . . . . . . . . . 66

D+ analysis in Pb-Pb collisions at √ sN N = 2.76 TeV at the LHC with ALICE. . . . . . . . 66

Next-to-leading order analysis of inclusive jet, tagged jet and di-jet production in PbPbcollisions at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Reconstruction of Ds mesons in the ALICE Experiment at LHC . . . . . . . . . . . . . . 67

Dissipative dynamics of highly anisotropic plasmas . . . . . . . . . . . . . . . . . . . . . 68

Event anisotropy v2 of identified hadrons and light nuclei in Au+Au collisions at√sNN =7.7, 11.5 and 39 GeV with STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Centrality dependence of theΥNuclearModification Factor at√sNN = 200 GeVmeasuredwith STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

ix

Investigating jet and non-jet contributions to long range pseudo-rapidity correlations indi-hadron measurements from STAR. . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Leading hadron PID effects in di-hadron angular correlations in STAR . . . . . . . . . . 70

Charge fluctuations in chiral models and the QCD phase transition . . . . . . . . . . . . 71

Roles of Axial Anomaly on Neutral Strongly Interacting Matter —- New Critical Points atLow Temperature and the Absence of Chromomagnetic Instabilty —- . . . . . . . . . 71

J/psi analysis in proton+proton at 7 TeV in the ALICE muon spectrometer using a pT - ycorrection method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Search for the QCD Critical Point: Higher Moments of Net-proton, Net-charge MultiplicityDistributions from the RHIC Beam Energy Scan . . . . . . . . . . . . . . . . . . . . . 72

Multihadron production in hadronic and nuclear collisions . . . . . . . . . . . . . . . . . 73

Prospects for charm RAA in PbPb collisions at LHC via D0->Kpi reconstruction in ALICE 73

STAR science for the coming decade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Development of the CBM RICH detector . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Dynamical equilibration of strongly-interacting ’infinite’ parton matter within a Parton-Hadron-String Dynamics (PHSD) transport approach . . . . . . . . . . . . . . . . . . 75

Jets in QCD media: from color coherence to decoherence . . . . . . . . . . . . . . . . . . 75

Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC . . . . . . . . . 76

Dissipative hydrodynamics for relativistic multi-component systems . . . . . . . . . . . 77

Linear confinement and phase transitions in holographic QCD . . . . . . . . . . . . . . . 77

From RHIC to LHC: heavy quarks and J/psi in a partonic transport model . . . . . . . . . 77

Percolation of Color Sources and the Equation of State of QGP in central Au-Au collisionsat √sNN =200 GeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Open charm hadron measurement in pp and Au+Au collisions at√s = 200 GeV in STAR 78

A High Level Online Tracking Trigger for the STAR experiment at RHIC . . . . . . . . . 79

Relativistic fluid dynamics from the Boltzmann equation: going beyond the 14-momentapproximation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Determination of relaxation times at weak and strong coupling . . . . . . . . . . . . . . 80

Dielectron Continuum Production from√sNN = 200 GeV pp and Au+Au collisions at STAR

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Observation of the antimatter helium-4 nucleus . . . . . . . . . . . . . . . . . . . . . . . 82

Commissioning and detector performance of the VTX-Pixel detector for RHIC-PHENIXexperiment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

x

STAR measurements of bottom to charm ratio and heavy quark interaction with the QCDmedium through non-photonic electron-hadron correlations . . . . . . . . . . . . . . 82

Inclusive charged hadron elliptic flow in Au + Au collisions at√sNN = 7.7, 11.5 and 39 GeV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Probing the gluonic structure of matter at a future Electron-Ion Collider . . . . . . . . . 83

Directed flow of Identified Particles in Au+Au Collisions at √sNN= 39, 11.5 and 7.7 GeVfrom the STAR Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Charge-to-Neutral fluctuation in AuAu collisions at Forward rapidity at RHIC. . . . . . . 84

Viscous hydrodynamic evolution with non-boost invariant flow for the color glass conden-sate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Hydrokinetic predictions for femtoscopy scales in A+A collisions in the light of recentALICE LHC results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Mach Cones and Two-Particle Correlations: The Origins in a Kinetic Transport Approach 86

Shear Viscosity of the QGP in Central A-A Collisions at RHIC and LHC Energies in theColor String Percolation Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Finite lifetime effects on the photon production from a quark-gluon plasma . . . . . . . 87

Elliptic Flow of charged particles in Au+Au collisions at√sNN = 7.7, 11.5 and 39 GeV fromSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Low-mass meson production through di-leptonic decays in p+p and Au+Au collisions at√sNN = 200 GeV from STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Chirality, magnetic field and parity violation in hot QCD matter . . . . . . . . . . . . . . 88

Leptonic decay of phi(1020) meson measured with the STAR experiment . . . . . . . . . 89

Finite-size scaling search for the critical endpoint of QCD in heavy ion data . . . . . . . 89

Identified hadron production from the RHIC beam energy scan program in the STAR ex-periment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Multiparticle system in high energy hadronic/nuclear collision and matter state of earlyuniverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Viscous relaxation time in relativistic hydrodynamics . . . . . . . . . . . . . . . . . . . . 91

Energy dependence of the freeze out eccentricity from azimuthal dependence of HBT atSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

D0 meson production in pp collisions at the LHC with ALICE and prospects for charm flowmeasurements in PbPb collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Phenomenological interpolation of inclusive J/psi production to proton-proton collisionsat sqrt(s)=2.76 TeV and 5.5 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Direct photons at low transverse momentum – a QGP signal in pp collisions at LHC . . 92

xi

Exploring compressed nuclear matter with HADES . . . . . . . . . . . . . . . . . . . . . 93

Dynamics near QCD critical point by dynamic renormalization group . . . . . . . . . . . 94

QCD Phase Diagram based on Strong Coupling Lattice QCD . . . . . . . . . . . . . . . . 94

Sensitivity of the elliptic flow coefficient to a temperature-dependent shear viscosity-to-entropy density ratio in ultrarelativistic heavy-ion collisions at RHIC and LHC . . . 95

Chiral transition in a magnetic field and at finite baryon density . . . . . . . . . . . . . . 95

Suppression of large transverse momentum hadrons in central Pb+Pb collision at LHC . 96

Turbulent fluctuations around Bjorken flow . . . . . . . . . . . . . . . . . . . . . . . . . 96

Medium-induced modifications of color flow in high transverse momentum processes . . 97

Probing deconfinement with chiral effective models at imaginary chemical potential . . 97

Charmonium mass in hot and dense hadronic matter from QCD sum rules . . . . . . . . 98

Determining initial state fluctuations from flow measurements . . . . . . . . . . . . . . . 98

Understanding initial state fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Ratio of J/Psi to Rho Photoproduction Cross Sections at the Relativistic Heavy Ion Colliderwith STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Jet-Hadron Correlations in STAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Bulk viscosity in heavy-ion collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Lattice QCD based equation of state at finite baryon density . . . . . . . . . . . . . . . . 100

D0 production in p+p sqrts = 200 GeV collisions at STAR . . . . . . . . . . . . . . . . . 101

Transition temperature and the equation of state from lattice QCD, Wuppertal-Budapestresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Forward-Backward Multiplicity Correlations for Identified Particles at STAR . . . . . . . 102

Elliptic and triangular flow in the event-by-event 3+1D viscous hydrodynamics . . . . . 103

Spectrum of initial fluctuations in the little bang . . . . . . . . . . . . . . . . . . . . . . . 103

The STAR Upgrade Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Local baryon-strangeness correlation from hypernuclei and coalescence volume from lightnuclei in relativistic heavy ion collisions . . . . . . . . . . . . . . . . . . . . . . . . . 104

Spectrum of fermion coupled with massive vector boson at finite temperature in gaugeinvariant formalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Centrality dependence of viscous quark gluon plasma at LHC . . . . . . . . . . . . . . . 105

DynamicalK/π, p/π, andK/p fluctuations in √sNN = 7.7-200 GeV Au+Au collisions . 106

Correlations and fluctuations from lattice QCD . . . . . . . . . . . . . . . . . . . . . . . 107

xii

J/Psi production in proton-proton collisions at sqrt(s) = 2.76 TeV in the ALICE ForwardMuon Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Inhomogeneous phase during the chiral transition . . . . . . . . . . . . . . . . . . . . . . 107

Spectra, flow and HBT in PbPb collisons at the LHC . . . . . . . . . . . . . . . . . . . . . 108

Jet quenching and elliptic flow in heavy ion collisions at RHIC and LHC within a pQCD-based partonic transport model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Charge balance correlations and contributions to local parity violation observables . . . 109

Mix-ratios of Higher Order Moments of Proton and Kaon as a baseline of QCD CriticalPoint search at RHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Centrality dependence of muon tracking efficiency in the ALICE Forward Muon Spectrom-eter for Pb-Pb collisions at 2.76 TeV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Event-by-event hydrodynamics and elliptic flow from fluctuating initial state . . . . . . 110

Strongly intensive measures for chemical fluctuations in A+A and p+p collisions: statisticaland transport models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

AAMQS: a non-linear QCD description of new HERA data at small-x . . . . . . . . . . . 111

Heavy quarkonium measurements from PHENIX . . . . . . . . . . . . . . . . . . . . . . 112

Jet modification from RHIC to LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Polarization Effects at RHIC and LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Jet Quenching via Jet Collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Can transport peak explain the low-mass enhancement of dileptons at RHIC? . . . . . . 114

Higher moments of Net Kaon Fluctuation in the Beam Energy Scan of STAR . . . . . . . 114

QCD thermodynamics by numerical simulations of Lattice QCD with Wilson-type quarks 115

Signals from the QCD phase transition in the early universe . . . . . . . . . . . . . . . . 115

Heavy ion program at JINR NICA/MPD facility . . . . . . . . . . . . . . . . . . . . . . . 116

J/Psi production and correlation in p+p and R_AA at high-pt in Au+Au collisions . . . 116

Hadron Productions at LHC Energies with HIJING2.0 Model . . . . . . . . . . . . . . . . 117

Measurement of J/ψ photoproduction in ultra-peripheral Au+Au collisions at √sNN=200GeVusing the PHENIX detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Search for local strong parity violation in STAR using multiple observables . . . . . . . . 118

Vorticity and Chaos in Heavy Ion Collisions . . . . . . . . . . . . . . . . . . . . . . . . . 118

Topological interactions of non-Abelian vortices with quasi-particles in high density QCD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

J/ψ polarization in p+p collisions at√s = 200 GeV at STAR . . . . . . . . . . . . . . . . . 119

xiii

Relativistic theory of hydrodynamic fluctuations . . . . . . . . . . . . . . . . . . . . . . . 119

Study of Λ−Λ correlations and search for the H-dibaryon with the STAR detector at RHIC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Continuous Time Monte Carlo for QCD in the Strong Coupling Limit . . . . . . . . . . . 120

Radiative energy loss reduction in a plasma due to damping . . . . . . . . . . . . . . . . 120

Heavy quark diffusion from lattice QCD spectral functions . . . . . . . . . . . . . . . . . 121

Examining real-time functions on the lattice using inverse propagator and self-energy . 121

Local Parity Violation or Local Charge Conservation/Flow? A Reaction-Plane-DependentBalance Function Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Eccentricity and elliptic flow in proton-proton collisions from parton evolution . . . . . 122

Light meson production in d+Au collisions measured by PHENIX experiment at sqrt(s_NN)= 200 GeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Feasability study for a Muon Forward Tracker in ALICE . . . . . . . . . . . . . . . . . . 123

Quark recombination and heavy quark diffusion in hot nuclear matter . . . . . . . . . . 124

Dragging D mesons by hot hadrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Towards the realization of the CBM-Micro Vertex Detector: Technological challenges anddetector response simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Scale for the phase diagram of quantum chromodynamics . . . . . . . . . . . . . . . . . 125

Understanding the equilibration of matter from time-dependent correlator . . . . . . . . 125

Methods for extracting elliptic flow (v2) and cocktail fits of ρ0 vector-meson in STAR atRHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Charged Particle Ratios for p+p Collisions in √s = 62.4 GeV at RHIC . . . . . . . . . . . . 126

The thermal model on the verge of the ultimate test: the LHC data . . . . . . . . . . . . . 127

D meson reference spectra in pp collisions at√s = 2.76~TeV with ALICE . . . . . . . . 128

Search for the QCD critical point by higher moments of the net-charge multiplicity distri-bution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Interference effects in medium–induced gluon radiation . . . . . . . . . . . . . . . . . . 129

Ultrasoft Fermionic Mode in QED and QCD plasmas . . . . . . . . . . . . . . . . . . . . 129

Measurement of J/Ψ elliptic flow inAu+Au collisions at √sNN=200GeV in STAR experiment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Measurement of light vector mesons by PHENIX experiment at RHIC . . . . . . . . . . . 130

Charmonium production on fixed target with proton and lead beams of LHC . . . . . . . 131

xiv

Completion of mass production of silicon pixel ladders for PHENIX silicon vertex tracker(VTX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

Underlying event studies in d+Au collisions at√sNN=200 GeV from STAR . . . . . . . 132

Fluctuations and the Ridge from RHIC to LHC . . . . . . . . . . . . . . . . . . . . . . . . 133

Measurement of Baryonic Resonances in pp Collisions at the LHC with ALICE . . . . . . 133

Direct photon production in heavy ion collisions in PHENIX experiment at RHIC . . . . 134

J/\psi production at mid-rapidity in pp collisions at \sqrts=7 TeV, measured with ALICE 134

QCD critical point and event-by-event fluctuations . . . . . . . . . . . . . . . . . . . . . 135

Measurement of dNch/deta with the ALICE VZERO detector in central Pb-Pb collisions at2.76 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Reconstruction and first observation of the charmed baryon Λc in pp collisions at √s = 7TeV with ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Equilibration in classical Yang-Mills dynamics . . . . . . . . . . . . . . . . . . . . . . . . 136

Critical behavior of Binder-like ratios and ratios of higher cumulants of conserved chargesin QCD deconfinement phase transition . . . . . . . . . . . . . . . . . . . . . . . . . 136

Identifying multi-quark hadrons from heavy ion collisions . . . . . . . . . . . . . . . . . 137

Extended Schematic Model for Hadrons, and What Happens to the Radius of an ExcitedHadron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Fluctuation, dissipation, and thermalization in non-equilibrium AdS5 black hole geome-tries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

A Forward Calorimeter (FoCal) as upgrade for the ALICE Experiment at CERN . . . . . 139

Nonperturbative Particle Production in Boost-Invariantly Expanding Electric Fields andTwo-Particle Correlations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Contribution from hard partons to the bulk elliptic flow . . . . . . . . . . . . . . . . . . 140

The ALICE Inner Tracking System: performance with proton and lead beams . . . . . . 140

Hunting electrons from heavy-flavour hadron decays with the ALICE Transition RadiationDetector in proton-proton collisions at √s = 7 TeV . . . . . . . . . . . . . . . . . . . . 141

Nuclear suppression at non-zero baryonic chemical potential . . . . . . . . . . . . . . . . 141

New results on event-by-event ratio fluctuations in PbPb collisions at CERN SPS energies 142

Jet studies in 200 GeV d+Au collisions from the STAR experiment at RHIC . . . . . . . . 142

Charged particle productionwith respect to the Reaction Plane in Pb-Pb collisions at√sNN=

2.76 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Dilepton production in heavy-ion collisions within the parton hadron string dynamics(PHSD) transport approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

xv

Deconfinement and chiral symmetry in effective models with fermions in higher represen-tations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Flow analysis with event-plane method using the VZERO detector in Pb-Pb collisions atsqrt(sNN)=2.76 TeV collected by the ALICE experiment at the LHC . . . . . . . . . . 144

Pion production in p+p and p+C interactions at 31 GeV/c . . . . . . . . . . . . . . . . . . 145

Distortion of photon HBT image by the vacuum birefringence in strong magnetic field . 145

Identified particle v3 measurements at 200GeV Au+Au collisions at RHIC-PHENIX experi-ment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Upgrade of ALICE Electromagnetic Calorimeter to enhance di-jet measurements . . . . 146

Pseudorapidity dependence of charged hadron multiplicity and transverse energy densitiesin PbPb collisions from CMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Charged hadron azimuthal anisotropy (v_2) in sqrtsNN = 2.76 TeV PbPb collisions fromCMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Weak boson production measured in PbPb and pp by CMS . . . . . . . . . . . . . . . . . 148

Centrality and transverse momentum dependence of the nuclear modification of chargedparticle spectra in PbPb collisions at 2.76 TeV from CMS . . . . . . . . . . . . . . . . 148

Measurement of inclusive isolated photons in PbPb collisions with CMS . . . . . . . . . 149

Rapidity and centrality dependence of transverse energy distributions in PbPb collisionsfrom CMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Study of jet quenching using dijets in PbPb Collisions with CMS . . . . . . . . . . . . . . 150

Dijet fragmentation functions measured in PbPb collisions with CMS . . . . . . . . . . . 150

The dynamics of quark droplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

Monte-Carlo simulation for elastic energy loss of high-energy partons in a hydrodynamicalbackground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

Jet reconstruction with particle flow in heavy-ion collisions with CMS . . . . . . . . . . 151

Charmonium production measured in PbPb and pp collisions by CMS . . . . . . . . . . . 152

Bottomonium production measured in PbPb and pp collisions by CMS . . . . . . . . . . 152

Observation of a ridge correlation structure in high multiplicity pp collisions with CMS . 153

Dihadron correlations in PbPb collisions at √sNN = 2.76 TeV with CMS . . . . . . . . . . 153

Measurement of higher order flow harmonics in PbPb collisions at √sNN = 2.76 TeV byCMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Electron reconstruction and Z measurement in the di-electron channel in PbPb collisionswith CMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

xvi

Study of beauty production in pp collisions at√s = 7 TeV with ALICE, using displaced

electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Readout of the CMS experiment during the 2010 heavy ion run . . . . . . . . . . . . . . 155

Performance of the CMS Zero Degree Calorimeter for PbPb and pp running . . . . . . . 155

B → J/ψ measurement in PbPb at √s_NN = 2.76 TeV using CMS . . . . . . . . . . . . . . 156

Data-driven efficiencies for di-muon measurements in heavy ion collisions with CMS . . 156

Effect of the polarization on the acceptance for quarkonia studies in PbPb at √sNN = 2.76TeV in CMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

Performance of PHENIX HBD in Au + Au central collisions . . . . . . . . . . . . . . . . . 157

Quarkonia propagation and collectivity in the QGP: Towards the suppression of quarkoniasuppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

ALICE detector upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Large-N_c behavior of hadronic models at nonzero temperature . . . . . . . . . . . . . . 158

Construction and Installation of the PHENIX silicon pixel vertex tracker . . . . . . . . . 159

Forward and Backward toMid-Rapidity CorrelationsMeasured in d+AuCollsions at√SNN =

200 GeV with the PHENIX Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Particle identification in the ALICE experiment . . . . . . . . . . . . . . . . . . . . . . . 160

U(1)A anomaly effects on phase diagrams in chiral random matrix model . . . . . . . . . 160

The Level-0 trigger of the ALICE Electromagnetic Calorimeter . . . . . . . . . . . . . . . 161

Charmonium spectral functions at finite momenta in the quark-gluon plasma from latticeQCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions at LHC . . . . . 162

Influence of tubular initial conditions on two-particle correlations . . . . . . . . . . . . . 162

Using separated bottom and charm contribution to pin down the role of radiative energyloss for heavy quarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

Particle multiplicities in high-energy hadronic collisions at RHIC/LHC fromCGCwith localrcBK evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Global characteristics, long-range correlations, ridge and femptoscopic radii in pp-collisionsat LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Dimuon pairs from In-In collision at √sNN = 17.3 GeV at SPS energies . . . . . . . . . 165

Nuclear suppression at large pT and xF: Direct photons from RHIC to LHC . . . . . . . . 165

Measurement of neutral mesons at ALICE by means of one photon detected in electromag-netic calorimeter and another from its conversion in central tracking system . . . . . 166

xvii

Low pT direct photon production in 200GeV d+Au collisions measured by the PHENIXdetector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

Studies for an upgrade of the ALICE Inner Tracking System . . . . . . . . . . . . . . . . 167

Feasibility study of muon chamber for CBM experiment at FAIR . . . . . . . . . . . . . . 168

D meson production cross sections in pp collisions at √s = 7 TeV, measured with the ALICEdetector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

Lattice study of the second order transport coefficients . . . . . . . . . . . . . . . . . . . 169

Study of pion-pion correlations at LHC and RHIC energies in pp collisions within the quark-gluon string model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

A comprehensive study of the high-pt particle correlations in pp collisions at LHC/ALICE 169

Charmonium and open-charm production in p-A collisions at the SPS . . . . . . . . . . . 170

Measurement of Low Mass Electron-Positron Pairs with ALICE . . . . . . . . . . . . . . 170

Dissipative effect on the thermal photon spectra . . . . . . . . . . . . . . . . . . . . . . . 171

Femtoscopy of the proton-proton collisions at the LHC with pion-pion Bose-Einstein cor-relations in ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Resonance measurement in pp and PbPb collisions at LHC with the ALICE detector . . . 172

K0sK0s correlations in 7 TeV proton+proton collisions from the ALICE experiment at theLHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Jet Reconstruction and Jet Background Classification with the ALICE experiment in PbPbcollisions at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Nuclear modification of charm quarks in Pb-Pb collisions at √sNN=2.76 TeV at LHC . . 173

K0s and Lambda production in PbPb collisions with the ALICE experiment . . . . . . . . 174

Unintegrated gluon distributions and k_t-factorization in forward hadron production inDIS and pA collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

Multi-strange particle measurements in 7 TeV proton-proton and 2.76 TeV PbPb collisionswith the ALICE experiment at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . 175

The next decade of physics with PHENIX . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

Elliptic flow at high transverse momentum in PbPb collisions at √sNN = 2.76~TeV withthe ALICE experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

Pt spectra of hadrons identified with the ALICE Inner Tracking System . . . . . . . . . . 176

Measurement of J/psi production at forward rapidity in pp collisions at sqrt(s)= 2.76 and 7TeV with ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

Electrical conductivity and thermal dilepton rate from quenched lattice QCD. . . . . . . 177

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Measurement of π/K/p spectra with ALICE in proton-proton collisions at√s = 900 GeV

and√s = 7 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Photons at RHIC and at the LHC: the role of viscosity and of event-by-event fluctuations 177

Anisotropic flow of charged particles at 2.76 TeV measured with the ALICE detector . . 178

Measurements of low mass dielectrons in Au+Au collisions with the HBD upgrade of thePHENIX detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

Heavy-flavor production cross section in the semi-electronic channel at mid-rapidity in ppcollisions at sqrt(s)=7 TeV with ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Collision energy dependence of the flow and spectra results in Au+Au collisions at √sNN

= 7.7-200 GeV from PHENIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

New experiments for study of in-medium vector mesons at J-PARC . . . . . . . . . . . . 180

Energy dependence of energy loss in Au+Au collisions at PHENIX . . . . . . . . . . . . 180

Pseudorapidity density of charged particles and its centrality dependence in Pb-Pb colli-sions at √sNN = 2.76 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

System-size dependence of particle ratio fluctuations in Pb+Pb collisions at 158 AGeV . . 181

LHC results on femtoscopic pi+pi correlations from the UrQMD transport approach . . . 182

Validity of the hadronic freeze-out curve . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Derivation of Causal Relativistic Hydrodynamic Equations and Novel Moment Method . 183

Recent PHENIX results on open heavy flavor . . . . . . . . . . . . . . . . . . . . . . . . . 184

Triangular flow and nonflow by 2-, 4-, and 6-particle cumulants from STAR . . . . . . . 184

Midrapidity charged particle directed flow in PbPb collisions at sqrts_NN = 2.76 TeVmeasured with ALICE at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Photonuclear interactions in ultra-peripheral Pb+Pb collisions at the LHC . . . . . . . . 185

Event-by-event mean pT fluctuations in pp and PbPb collisions measured by the ALICEexperiment at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

Shear viscosity in a partonic cascade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

My suppression, your flow, his Cronin - our insight . . . . . . . . . . . . . . . . . . . . . 186

PHENIX measurements of higher-order flow harmonics in Au+Au collisions at √sNN =200 GeV: implications for Initial-eccentricity models and the specific viscosity of theQuark Gluon Plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

Charged-particle transverse momentum spectra in proton-proton collisions at √s = 0.9 TeV,2.76 TeV and 7 TeV measured with ALICE at the LHC . . . . . . . . . . . . . . . . . . 187

Electromagnetic superconductivity of vacuum in strong magnetic field and heavy ion col-lisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

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Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decaysat Mid-Rapidity in Pb-Pb Collisions at sqrt(s_NN)=2.76 TeV with ALICE . . . . . . . 188

Charmonium dynamics in the UrQMD transport model . . . . . . . . . . . . . . . . . . . 188

Net-baryon-, net-proton-, and net-charged particle kurtosis in heavy-ion collisions withina relativistic transport approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

Photoproduction of Vector Mesons in Ultra-Peripheral Pb-Pb Collisions at the LHC . . . 189

Measurement of J/ψ → e+e− Production in Pb-Pb Collisions at √s = 2.76 TeV with ALICEat the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

J/psi production at forward rapidity in PbPb collisions at sqrt(s_NN) = 2.76 TeV, measuredwith the ALICE detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Low mass dimuon production in proton-nucleus collisions at√s = 27.5~GeV with the

NA60 experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Study of central production in pp-collisions at √s=7 TeV with the ALICE experiment . . 191

Production of neutral pions and eta-mesons in pp collisions measured with ALICE . . . 192

Measurement of the Multiplicity Dependence of J/ψ → e+e− Production in √s = 7 TeV ppCollisions with ALICE at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

Charge dependent azimuthal correlations in PbPb collisions at √sNN = 2.76~TeV . . . . 193

Vector meson production in pp collisions at sqrt(s)=7 TeV, measured with the ALICE detec-tor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Constraining Cold Nuclear Matter Effects on J/ψ production in Au +Au Collisions . . . 194

Measurements of Bose-Einstein correlations at LHC with CMS . . . . . . . . . . . . . . . 194

MEASUREMENTOF SINGLE-MUONAND J/\psi PRODUCTIONAT FORWARDRAPIDITYAS A FUNCTION OF THE COLLISION MULTIPLICITY IN PP COLLISIONS AT \sqrts= 7 TeV WITH ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

Suppression of neutral pion production at large transverse momentum measured with theALICE experiment in PbPb collisions at √sNN=2.76 TeV . . . . . . . . . . . . . . . . 195

Production of nuclei and anti-nuclei in pp and Pb-Pb collisions with ALICE at the LHC . 195

Charged particle production at large transversemomentum in PbPb collisions at sqrt(s)=2.76TeV measured with ALICE at the LHC. . . . . . . . . . . . . . . . . . . . . . . . . . . 196

Transverse sphericity in minimum bias proton-proton collisions at√s = 0.9 and 7 TeV with

ALICE at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

Measurement of J/psi polarization at forward rapidity in pp collisions at sqrt(s)=7 TeV withthe ALICE detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

Topological reconstruction of strange hadrons in Pb-Pb collisions with the ALICE experi-ment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

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Inclusive photon production at forward rapidities for pp collisions at √s = 0.9 TeV and 7TeV in ALICE at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

Photoproduction of J/Psi in Ultra-Peripheral Pb+Pb collisions at sqrt(s_NN)=2.76 TeV inALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Diffraction dissociation of protons in proton-proton collisions at \sqrts = 0.9 TeV, 2.76 TeVand 7 TeV with ALICE at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Cold Nuclear Modification of J/psi Production in d+A and A+A Collisions . . . . . . . . 199

Measurement of inclusive neutral pion yields in in p+p and Pb+Pb collisions at √sNN=2.76TeV with the ALICE EMCal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

Nonequilibrium effects at the phase transition in chiral fluid dynamics including dissipationand noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

High-pT suppression of Lambda and K0s in PbPb collisions at sqrt(sNN) = 2.76 TeV withALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

Triggered di-hadron correlations in PbPb collisions from the ALICE experiment . . . . . 200

Elliptic Flow from the Parton-Hadron-String-Dynamics . . . . . . . . . . . . . . . . . . . 201

Multiplicity Dependent Di-Hadron Correlations Measured with ALICE at the LHC . . . 201

Anomalous baryon production and its interplay with jet energy loss at RHIC and LHCenergies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

A data driven validation of the Pythia jet cross section in pp collisions at√s = 2.76 TeV 202

Charged KK femtoscopy correlations from 7 TeV pp collisions measured by ALICE collab-oration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Untriggered di-hadron correlations in PbPb \sqrts_NN =2.76 TeV collisions from the AL-ICE experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Measurement of Upsilon suppression in Au+Au collisions at 200 GeV . . . . . . . . . . . 204

Evaluation of the identification efficiency of the ALICE HMPID detector in p-p collisionsat √s = 7 TeV by means of V0 decays . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

Energy dependence of π0 suppression in Au+Au collisions . . . . . . . . . . . . . . . . . 204

The influence of bulk evolution models on heavy-quark phenomenology . . . . . . . . . 205

Azimuthal anisotropy of neutral pion production in Pb+Pb collisions at sqrt(s_NN) = 2760GeV measured by ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

Modeling heavy ion collisions with CHIMERA . . . . . . . . . . . . . . . . . . . . . . . . 206

Identified particles from viscous hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . 206

The Rise and Fall of the Ridge at RHIC and the LHC . . . . . . . . . . . . . . . . . . . . . 207

Three particle correlations as a probe of eccentricity fluctuations . . . . . . . . . . . . . . 207

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Heavy ion initial conditions and correlations between highermoments in the spatial anisotropy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

Measurement of the electromagnetic dissociation cross-section of Pb nuclei at 2.76 A Tevwith the ALICE ZDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

Elliptic and triangular flow of identified particles measured with the ALICE detector. . . 209

Jet production measurements with the ALICE Experiment in pp collisions at the LHC . . 209

Measurement of Charge Multiplicity Asymmetry Correlations to Search for Chiral Mag-netic Effect in Heavy Ion Collisions by STAR . . . . . . . . . . . . . . . . . . . . . . . 209

Ridge Studies in Pb+Pb Collisions at the LHC based on Number and TransverseMomentumTwo-Particle Correlation Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Charge Fluctuations in Pb-PbCollisions at √sNN= 2.76 TeVmeasured byALICE experiment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Towards the phase diagram of QCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

Femtoscopy of the system shape fluctuations in heavy ion collisions . . . . . . . . . . . . 211

Two-pion Bose-Einstein correlations in PbPb collisions at 2.76 TeV with ALICE . . . . . 212

Probing nuclear matter with jets and γ-hadron correlations: results from PHENIX . . . . 212

Status of the Search for Hadronic Squeezed Correlations at RHIC Energies . . . . . . . . 212

D meson nuclear modification factors in PbPb collisions at √sNN = 2.76 TeV, measuredwith the ALICE detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Transverse momentum distributions of pions, kaons and protons for high multiplicity andclose to azimuthal isotropic events in 7 TeV pp collisions with the ALICE experimentat the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Rapidity and centrality dependence of identified hadrons in Au+Au and p+p collisions at200 GeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Development of the FARICH detector as a possible upgrade for ALICE HMPID system . 215

Droplets in the cold and dense chiral phase transition . . . . . . . . . . . . . . . . . . . . 215

Long-Range (Forward-Backward) Pt and Multiplicity Correlations in pp Collisions at 0.9and 7 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

Cold nuclear matter physics at low-x from d+Au collisions at PHENIX . . . . . . . . . . 217

Jets and Underlying Events in p+p Collisions at LHC energies . . . . . . . . . . . . . . . 217

Charged-particle multiplicity, centrality and the Glauber model with ALICE at 2.76 ATeV 218

Coulomb effects in relativistic heavy ion collisions from CBM experiment . . . . . . . . 218

Exact analytic hydrodynamical results and estimations of the initial conditions in p+p andPb+Pb collisions at LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

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Cross section normalization in ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

Proposal of new super-compact calorimeter design for the forward physics . . . . . . . . 219

Measurement of electrons from heavy-flavor decays in p-p and Pb-Pb collisions with theALICE EMCAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

Hadron-Resonance Correlation in pp collisions at the LHC with ALICE . . . . . . . . . . 220

Di-electron analysis in Au+Au collisions using the PHENIX Hadron Blind Detector . . . 221

Effect of running coupling on photons from jet - plasma interaction in relativistic heavyion collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

Nuclear modification factor in an anisotropic Quark-Gluon-Plasma . . . . . . . . . . . . 222

Open heavy flavor physics in the muon channel with ALICE in pp collisions at 7 TeV andPbPb at 2.76 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

Underlying Event measurement in pp collisions with the ALICE experiment at LHC . . . 223

Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV, 2.76 TeV and 7TeV, with ALICE at LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

Initial condition fluctuations in heavy ion collisions . . . . . . . . . . . . . . . . . . . . . 224

Detector effects and systematic uncertainties in the directed flow measurement with spec-tator neutrons in ALICE at LHC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

The ALICE EMCal Overview and Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

Characterizing cold nuclear matter effects through dielectrons in d+Au collisions at √NN= 200 GeV at PHENIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

Projectile Spectator Detector for the heavy ion program of the NA61/SHINE experiment atthe CERN SPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

Identified particle flow methods in ALICE at the LHC . . . . . . . . . . . . . . . . . . . . 226

A Design for a Novel TOF Detector with 10 picosecond Resolution . . . . . . . . . . . . 226

Propose of studying the symmetry energy of asymmetric nuclearmatter under super-saturationdensity at the Cooling Storage Ring at Lanzhou . . . . . . . . . . . . . . . . . . . . . 226

Azimuthal correlation between photon/π0 and charged hadrons with the ALICE experi-ment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Neutral Pion production in PbPb collisions at sqrt(s_NN)=2.76 TeV measured by ALICE viaphoton conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Measurement of pi0 production in p+p collisions at sqrt( s ) = 7 TeV with the ALICE EMCal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

Studies of ω(782) → π0γ → 3γ in p+p collisions at √s = 7 TeV with the ALICE electromag-netic calorimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

xxiii

Measurement of eta meson production in pp collisions at √s = 7 TeV with the ALICE elec-tromagnetic calorimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

pi0 and eta meson production in pp collisions at 0.9, 2.76 and 7 TeV measured with ALICEPHOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

Correlation Between Mean pT and Charged Particle Multiplicity in pp Collisions at √s =0.9, 2.76 and 7 TeV with ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

Energy density in Pb-Pb Collisions at LHC . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Transverse energy measurements with ALICE in pp and Pb-Pb collisions . . . . . . . . . 230

Ridge Studies in Pb-Pb Collisions at the LHC based on Number and Transverse MomentumTwo-Particle Correlation Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

Three-Particle Jet-Like Correlations in Pb-Pb Collsions at sqrt(s_NN)=2.76 TeV at ALICE 231

Prompt and detached J/psi production in p–p collisions at Sqrt(s) = 7 TeV with the ALICEdetector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

Production of NeutralMesons Identified byALICE-PHOS in Pb-Pb collisions at sqrts_NN=2.76TeV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

R&D on MRPC for STAR MTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

Femtoscopy of PbPb and pp collisions at the LHC with the ALICE experiment . . . . . . 233

Flow - Theory perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233


Fluctuations & correlations – TH perspective . . . . . . . . . . . . . . . . . . . . . . . . . 234

Results from correlation studies in ALICE . . . . . . . . . . . . . . . . . . . . . . . . . . 234

Jet yield enhancement in high-tower trigger eventswith theALICE Electromagnetic Calorime-ter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

STAR correlations and fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234


Presentation of QM12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Closing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

ALICE vertexing performance and charm reconstruction . . . . . . . . . . . . . . . . . . 235

Preparation for open charm elliptic flow measurement via D-meson decay to hadrons withALICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Probing the gluonic structure of matter at a future Electron-Ion Collider . . . . . . . . . 236

eA collisions at the Large Hadron-electron Collider . . . . . . . . . . . . . . . . . . . . . 236

Proposal for QM13/14 in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

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Preparation of QM2012 at Washington . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Proposal for QM13/14 in Darmstadt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Leptonic observables in sqrt(s_NN)=2.76 TeV PbPb collisions measured with the ATLASdetector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Proposal for QM13/14 in Bologna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV and 7 TeV, withthe ALICE Forward Multiplicity Detector at LHC . . . . . . . . . . . . . . . . . . . . 237

Charged pion spectra at high pT measured via dE/dx with the ALICE TPC . . . . . . . . 238

Charged pion spectra at high pT measured via dE/dx with the ALICE TPC . . . . . . . . 238

Proposal for a QM in Brazil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

QM2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

First B→J/ψ measurement in PbPb collisions at 2.76 TeV with the CMS detector . . . . . 239

First measurement of Upsilon suppression . . . . . . . . . . . . . . . . . . . . . . . . . . 239

pending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decaysat Mid-Rapidity in Pb-Pb Collisions at 2.76 TeV with ALICE . . . . . . . . . . . . . . 239

Probing nuclear parton densities and parton energy loss processes through photon + heavy-quark jet production in p-A and A-A collisions . . . . . . . . . . . . . . . . . . . . . . 239

Dimuon radiation at the CERN SPS within a hybrid evolution model . . . . . . . . . . . 239

Local Parity Violation or Local Charge Conservation/Flow? . . . . . . . . . . . . . . . . 240

Production of (anti)nuclei in pp and PbPb collisions with ALICE at the LHC . . . . . . . 240

Continuous Time Monte Carlo for QCD in the Strong Coupling Limit . . . . . . . . . . . 240

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QM 2011 - XXII International Conference on Ultrarelativistic Nucleus-… / Book of Abstracts

Board: 1 / 34

Tagging of eta decay products in Bose-Einstein correlations to an-alyze chiral restorationAuthor: Máté Csanád1

Co-author: Mónika Kőfaragó 1

1 Eötvös University

In case of chiral U_A(1) symmetry restoration the mass of the eta’ boson (the ninth, would-be Gold-stone boson) is decreased, thus its production cross section is heavily enhanced. The eta’ decays(through one of its decay channels) into five pions. These pions will not be correlated in terms ofBose-Einsten correlations, thus the production enhancement changes the strength of two-pion corre-lation functions at lowmomentum. Preliminary results strongly support themass decrease of the eta’boson. In this paper we propose a method to select pions coming from eta’ decays. We investigatethe efficiency of the proposed kinematical cut in several collision systems and energies with severalsimulators. We prove that our method can be used in all investigeted collision systems.

Board: 2 / 35

Equation of state and initial temperature of quark gluon plasmaat RHICAuthor: Mate Csanad1

Co-author: Imre Májer 1

1 Eötvös University

In gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) a perfect fluid of quarks, some-times called the strongly interacting quark gluon plasma (sQGP) is created for an extremely shorttime. The time evolution of this fluid can be described by hydrodynamical models. After expansionand cooling, the freeze-out happens and hadrons are created. Their distribution reveals informationabout the final state of the fluid. To investigate the time evolution one needs to analyze penetrat-ing probes, such as direct photon spectra. Distributions of low momentum photons was publishedin 2010 by PHENIX. Such low momentum distributions can be compared to hydrodynamics to de-termine the equation of state and the initial temperature of sQGP. In this paper we analyze a 3+1dimensional solution of relativistic hydrodynamics. We calculate momentum distribution of lowmomentum thermal photons and other observables from the model. Using earlier fits of this modelto hadronic spectra, we compare photon calculations to measurements from RHIC. We find that theinitial temperature of the center of the fireball is at least 519+-12 MeV, while for a time averagedequation of state we get c_s=0.36+-0.02. We also find an interesting shape of direct photon ellipticflow.

Board: 131 / 37

The phase diagram in T-mu-Nc spaceAuthor: Giorgio Torrieri1

Co-authors: Igor Mishustin 2; Stefano Lottini 2

1 JW Goethe Universitat, Frankfurt2 FIAS

Page 1


Corresponding Author: [email protected]

We argue that a so far neglected dimensionless scale, the number of neighbors in a closely packedsystem (Nn, Nn~10 in our world), is relevant for the convergence of the large number of colors (Nc,Nc=3 in our world) expansion at large chemical potential.

Using a highly simplified but universal model, we demonstrate that the Nc≫Nn limit is qualitativelydifferent from our world’s Nc≪Nn. In particular, the relationship between deconfinement and per-colation, and the in-mediummodification of baryonic wavefunctions, are very different in these tworegimes.

We explore phenomenological consequences of these findings, particularly in regard to the new“Quarkyonic” phases conjectured from large Nc arguments and the problem of chiral symmetrybreaking at high chemical potential

Based on developments from Phys.Rev.C82:055202,2010and http://arxiv.org/abs/1103.4824

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Soft-quark bremsstrahlung and energy lossesAuthor: Yuri Markov1

Co-author: Margarita Markova 1

1 Institute for System Dynamics and Control Theory


Within the framework of a semiclassical approximation the general theory of calculation of effectivecurrents and sources generating bremsstrahlung of an arbitrary number of soft quarks and soft glu-ons at collision of a high-energy color-charged particle with thermal partons in a hot quark-gluonplasma, is developed. For the case of one- and two-scattering thermal partons with radiation ofone or two soft excitations, the effective currents and sources are calculated in an explicit form. Inthe model case of ‘frozen’ medium, approximate expressions for energy losses induced by the mostsimple processes of bremsstrahlung of soft quark and soft gluon, are derived.

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On the fluctuation-dissipation theorem for soft fermionic excita-tions in a hot QCD plasmaAuthor: Margaret Markova1

Co-author: Yuri Markov 1

1 Institute for System Dynamics and Control Theory


Two ways of deriving the fluctuation-dissipation theorem (FDT) for soft fermion excitations in ahot non-Abelian plasma being in a thermal equilibrium are discussed. The first of them is based onthe extended (pseudo)classical model in describing a quark-gluon suggested by us, while the secondone rests on the standard technique of calculation of the FDT for thermodynamically equilibriumsystems. It is shown that the full accounting all subtleties that are common to the fermion systemunder consideration , results in perfect coincidence of thus obtained FDTs. This provides a ratherstrong argument for the validity of the pseudoclassical model suggested.

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Theory developments / 42

Next-to-leading order structure function for DIS off a large nu-cleusAuthor: Giovanni Antonio Chirilli1

1 Lawrence Berkeley National Laboratory (LBNL)


The high-energy behavior of amplitudes in gauge theories can be reformulated in termsof the evolution of Wilson-line operators. In the leading order this evolution is governed by thenon-linear Balitsky-Kovchegov (BK) equation.In order to see if this equation is relevant for existing or future DIS accelerators(like EIC or LeHC) one needs to know how large are the next-to-leading order (NLO) corrections.In addition, the NLO corrections define the scale of the running-coupling constant in the BK equationand therefore determine the magnitudeof the leading-order cross sections.To obtain then the structure function for DIS off a large nucleus at the NLO accuracy in αs,we calculate the NLO contribution to the BK equationand the NLO photon impact factor,related to the probability of the virtual photon to split in a quark anti-quark pair before scatteringoff the target.We obtain for the first time an analytic expression in coordinate space of the NLO photon impactfactor.

Jets / 43

Higher harmonic jet tomography as a probe of fluctuating initialcondition geometries in A+AAuthor: Barbara Betz1

Co-authors: Giorgio Torrieri 2; Miklos Gyulassy 1

1 Columbia University2 Frankfurt Institute for Advanced Studies


While 2nd Fourier harmonics of jet quenching have been thoroughly explored in the literature andshown to be sensitive to (1) the underlying jet path length dependence of energy loss and (2) thedifferences between the mean eccentricity predicted by Glauber and CGC/KLN models of initialconditions, the sensitivity of higher harmonics, v_n(p_T, b), to differences between the fluctuationspectrum of geometries has remained relatively unexplored.We demonstrate that higher azimuthal jet harmonics (n>2) ofR_AA(p_T,phi) and I_AA(p_T,phi) are remarkably insensitiveto the differences of geometrical density fluctuations comparing between Glauber and CGC/KLNmodels of the initial conditions. Therefore, the differential elliptic v_2(p_T) vs. v_2^(I_AA)(p_T) mo-ment correlation between the 2nd moment of monojet R_AA and dijet I_AA nuclear modificationsfactors remains the most sensitive probe to differentiate between Glauber and CGC/KLN initial statesQGP geometries.

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Flow-Driven Conical Correlations in Heavy-Ion Collisions

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Author: Barbara Betz1

Co-authors: Dirk-H. Rischke 2; Giorgio Torrieri 3; Jorge Noronha 1; Miklos Gyulassy 1

1 Columbia University2 Frankfurt University3 Frankfurt Institute for Advanced Studies


We use (3+1)-dimensional hydrodynamic simulations to describethe propagation of a jet through an opaque medium and to investigatethe underlying jet-medium interactions. We discuss that thedouble-peaked structure seen in the two-particle correlationsmeasured at the Relativistic Heavy Ion Collider (RHIC), suggested as a signal for the creation ofa Mach cone, can arise due to the averaging over many events in a transversally expanding back-ground. We find that the jet-induced away-side yields are quite insensitive to different energy andmomentum loss scenarios, different jet velocities, and system sizes. Our claim can be experimentallydistinguished from a ‘true’ Mach cone by analyzing hard-soft correlations induced by heavy-flavorjets, in particularby verifying that the double-peak structure stays the same evenif the heavy quarks move subsonically.

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The Single Flavor Color Superconductivity in a Magnetic Field.

Authors: Bo Feng1; Defu Hou2; Ping-Ping Wu2; Ren Hai-cang3

1 University od Texas at El Paso2 Central China Normal University3 Rockefeller University

Corresponding Authors: [email protected], [email protected]

We investigate the single flavor color superconductivity in a magnetic field. Because of the absenceof the electromagnetic Meissner effect, forming a nonspherical CSC phase, polar, A or planar, doesnot cost energy of excluding magnetic flux. We found that these nonspherical phases do occupy asignificant portion of the phase diagram with respect to magnetic field and temperature and may beimplemented under the typical quark density and the magnetic field inside a compact star.Published in Phys.Rev.Lett.105:042001,2010.

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The Subleading Term of the Strong Coupling Expansion of theHeavy-Quark PotentialAuthors: Defu Hou1; Ren Hai-cang2; Shao-xia Chu1; Zi-Qiang Zhang1

1 Central China Normal University2 Rockefeller University

Corresponding Authors: [email protected], [email protected], [email protected]

Applying the AdS/CFT correspondence, the expansion of theheavy-quark potential of the calN supersymmetric Yang-Mills

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theory at large Nc is carried out to the sub-leading term in thelarge ‘t Hooft coupling at both zero and nonzero temperatures. The strong couplingcorresponds to the semi-classical expansion of the string-sigmamodel, the gravity dual of the Wilson loop operator, with thesub-leading term expressed in terms of functional determinants offluctuations. The contribution of these determinants are evaluatednumerically.

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Mach Cone Induced by γ-Triggered Jets in High-Energy Heavy-Ion CollisionsAuthor: Yan Zhu1

1 University of Bielefeld


Medium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linearBoltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is thedeflection of both the jet shower and the Mach-cone-like excitation in an expanding medium thatis found to give rise to a double-peak azimuthal particle distribution with respect to the initial jetdirection. Such a deflection is the strongest for hadron-triggered jets which are often produced closeto the surface of a dense medium due to trigger bias and travel against or tangential to the radial flow.Without such trigger bias, the effect of deflection on γ-jet showers and their medium excitation isweaker. Comparative study of hadron and γ-triggered particle correlations can therefore reveal thedynamics of jet-induced medium excitation in high-energy heavy-ion collisions.

Global and collective dynamics / 49

The second act of hydro: shocks and sounds from initial pertur-bations and jetsAuthor: Edward Shuryak1

1 Stony Brook University


Recently there was significant progress in account for several lowerharmonics of the Little Bang”, especially the so called triangular flow,ascribed to fluctuations of the initial conditions. We discuss thisproblem more generally, combining many harmonics coherently intocertain patterns of sound propagation. Analytic solution for all harmonicsis found for the so calledGubser flow”, with complete Green functionobtained. Another source of perturbationswhich can be studied using our results are waves induced by quenching jets.We argue that for large energy loss shock waves should form, as well asthe so called jet/fireball edge, separating unperturbed and excited matter.We discuss how this edge should be visible experimentally, perhaps on \event-by-event basis.

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Viscous QCD matter at RHIC and LHC energies. Insights fromviscous hydrodynamics + hadron cascade hybrid approachAuthor: Huichao Song1

Co-authors: Steffen Bass 2; Tetsufumi Hirano 3; Ulrich Heinz 4

1 Lawrence Berkeley National Laboratory2 Duke University3 The University of Tokyo4 The Ohio State University

We present recent results from the newly developed hybrid codeVISHNU [1] which couples viscous hydrodynamics for the quark-gluon plasma (QGP) with a hadroncascade model for the late hadronic stage. By describing the hadronic rescattering and freeze-outstagemicroscopically, we improve on earlier purely hydrodynamicmodels which required additionaladjustable parameters to describe the transport and freeze-out characteristics of the hadron phase.By describing the QGP phase as a viscous rather than ideal fluid (as done in previous macroscopic +macroscopic hybrid codes), we account for the non-zero viscosity of the quark-gluon plasma whichwe can now determine empirically, without contamination from an incomplete treatment of the latehadronic dynamics, by comparing VISHNU results with experimental elliptic flow data.

Using the Monte-Carlo-Glauber or Monte-Carlo-KLN models togenerate event by event fluctuating initial entropy density profiles and averaging these profiles ei-ther in the reaction-plane (i.e. directly) or in the participant-plane (i.e. after recentering and rotatingeach event so that the main axes of its entropy density align), we generate smooth average initialconditions for viscous hydrodynamics which account in different ways for the event by event fluc-tuations in shape and orientation of the initial state of the collision fireball [2]. We find that theeccentricity scaled elliptic flow v2/ϵ is a universal function of charged multiplicity per unit overlaparea (1/S)(dNch/dy) that depends only on the QGP viscosity but not on the initialization models[3]. Comparing these universal curves with experimental measurements we find that the specificQGP viscosity (η/s)QGP is constrained to fall in the range 1 < 4π(η/s)QGP < 2.5where the widthof this range is entirely dominated by model uncertainties for the initial eccentricities [3]. Comparedto analysis based on pure viscous hydrodynamics this reduces the previously quoted robust upperlimit for (η/s)QGP by a factor 2.5. The same (η/s)QGP values extracted in [3] from the centralitydependence of the pT -integrated elliptic flow of all charged hadrons also provide, for the first time, aconsistently good simultaneous description of the pT spectra and differential elliptic flow v2(pT ) forcharged hadrons as well as identified pions and protons over the entire range of collision centralitiesin 200 A GeV Au+Au collisions [4].

[1] H. Song, S. Bass and U. Heinz, Phys. Rev. C, in press [arXiv:1012.0555].

[2] T. Hirano and Y. Nara, Phys. Rev. C79, 064904,(2009).

[3] H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, arXiv:1011.2783 [nucl-th].

[4] H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, arXiv:1101.4638 [nucl-th].

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Non-Extensive Approach to High-Energy CollisionsAuthor: Gergely Barnafoldi1

Co-authors: Gergely Kalmár 2; Károly Ürmössy 2; Tamás S. Biró 1

1 KFKI Research Institute for Particle and Nuclear Physics of the HAS2 Eötvös University

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Non-extensive thermodynamics is a novel and promising tool for the statistical interpretation ofhigh energy phenomena. In particular the experimental systems are far from the familiar canonicalstate. On the basis of generalized entropy and energy composition rules also Tsallis–Pareto-likedistributions can be obtained. Such distributions reproduce extremely well the various transversemomentum spectra in hadron-hadron collisions and in cosmic rays. However, the derivation andthe correct interpretation of the Tsallis-Renyi parameter are still unsolved questions.

We investigated several models to discover the non-extensive phenomena behind hadronization.Here we present our results for (i) a possible microcanonical generalization of the Tsallis distributionin e+e- collision, and (ii) the original Tallis Pareto-like distribution including QCD evolution ansatzfor the hadronization process.

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Momentum broadening in weakly coupled quark-gluon plasmas

Author: Mindaugas Lekaveckas1

Co-authors: Christopher Lee 1; Francesco D’Eramo 1; Krishna Rajagopal 1; Liu Hong 1

1 MIT


Jet quenching parameter is an important quantity in order to understand energy losses in heavyion collisions and to get insights into properties of deconfined quark-gluon plasmas. Soft CollinearEffective theory provides framework to define momentum broadening of probing quark/gluon andthus define jet quenching parameter as the expectation value of two space-like separated light-likeWilson lineswhich can be evaluated for the desiredmedium. In this workwe evaluate jet quenchingparameter at weak coupling for quark-gluon plasmas in thermal equilibrium using Hard ThermalLoop resummed effective thermal field theory.

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Radial and elliptic flow in LHC Pb+Pb collisions from viscous hy-drodynamicsAuthor: Chun Shen1

Co-author: Ulrich Heinz 1

1 The Ohio State University


Predictions and postdictions from viscous hydrodynamics for the transverse momentum spectraand differential elliptic flow for unidentified and identified charged hadrons from Pb+Pb collisionsat LHC energies, including their centrality dependence, will be presented. These predictions arebased on a global viscous hydrodynamic fit of soft hadron spectra and their anisotropies measuredin Au+Au collisions at RHIC, using a state-of-the-art equation of state, which accurately reproducesthe observed charged hadron, pion and proton spectra and their differential v_2(p_T) for all col-lision centralities in the range p_T<2 GeV. Assuming the same specific effective shear viscosityeta/s=0.20 for KLN initial conditions at RHIC and LHC, we obtain a good description of the softcharged hadron spectra in central Pb+Pb collisions at sqrts=2.76 A TeV, but slightly overpredictthe integrated charged hadron elliptic flow in measured by the ALICE Collaboration in non-central

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Pb+Pb collisions. We explore whether and how this can be remedied by allowing for a tempera-ture dependent change of the specific shear viscosity eta/s of the quark-gluon plasma in the newlyexplored higher temperature region probed at the LHC. In doing so, we expose a need for a morequantitative understanding of the early pre-equilibrium stage. Future comparisons of spectra andelliptic flow for identified hadrons at both sqrts=2.76 and 5.5 A TeV with predictions presented inthis talk will allow to further test the validity of the viscous hydrodynamic model and will shedadditional light on possible variations of the quark-gluon transport coefficients between RHIC andLHC energies.

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Direct Photons frommicroscopic+macroscopic hybridmodelAuthor: Bjørn Bäuchle1

Co-author: Marcus Bleicher 1

1 Frankfurt Institute for Advanced Studies


The microscopic transport model UrQMD and a micro+macro hybrid model are used to calculatedirect photon spectra from A+A-collisions at FAIR- and RHIC-energies. In the hybrid model, theintermediate high-density part of the nuclear interaction is described with ideal 3+1-dimensionalhydrodynamics, while the initial state and final state-scatterings are modelled in UrQMD. DifferentEquations of State of the matter created in the heavy-ion collisions are investigated and the resultingspectra of direct photons are shown. The emission patterns of direct photons in space and time arediscussed.

Heavy Flavors / 56

Massive QCD antenna radiation in mediumAuthor: Hao Ma1

Co-authors: Carlos Salgado 1; Konrad Tywoniuk 2; Néstor Armesto 1; Yacine Mehtar-Tani 1

1 Universidad de Santiago de Compostela2 Lund University

Mediummodifications of jets have previously been thoroughly studied by calculating the gluon radi-ation spectrum off a highly energetic quark traversing a hot and dense QCD medium. But the studyof the interference effects, the building block of the QCD jet calculation in vacuum, between differentradiators has been missing for quite a long time. In this work we calculate, in the eikonal approxima-tion, the gluon radiation spectrum off a quark-antiquark antenna passing through a deconfined QCDplasma with the masses of the quark and antiquark turned on. Themassive quark-antiquark antennainvolves both the dead cone effect and the Landau-Pomeranchuk-Migdal (LPM) effect, and takes intoaccount the correlation between both of the emitters leading to an additional strong suppression ofgluon radiation at angles smaller than the opening angle of the quark-antiquark pair. Furthermore,the quark-antiquark antenna spectrum is infrared divergent. We calculate the medium-induced en-ergy loss of heavy quarks (charm and bottom) and compare it to well-known results (BDMPS/GLV).The implications on jet quenching observables in heavy ion collisions are also discussed.


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The QGP shear viscosity: elusive goal or just around the corner?

Author: Ulrich Heinz1



The last two years have seen tremendous progress in the theoretical tools for extracting the specificshear viscosity of the quark-gluon plasma in the temperature range explored by heavy-ion collisionsat RHIC and LHC.The effects of viscosity on the transverse momentum spectra and differential ellip-tic flow and their interplay with other hydrodynamic parameters have been studied systematically[1]. A global viscous hydrodynamic fit to charged and identified hadron spectra and elliptic flowat all collision centralities in RHIC Au+Au collisions has been shown to successfully extrapolate toPb+Pb collisions at the LHC [2], providing a rather good first description of the elliptic flowmeasuredby the ALICE collaboration. Viscous relativistic hydrodynamics has been coupled to a microscopicdescription of the late hadronic rescattering and freeze-out stage [3,4], thus eliminating previouslarge uncertainties arising from strong dissipative effects in the hadronic phase [5] and allowing fora first tightly constrained extraction of the QGP shear viscosity from RHIC data [3,6]. The largestremaining uncertainty arises from poor theoretical control over the initial spatial eccentricity of thecollision fireball, and a lack of prospects to more tightly constrain this initial deformation theoret-ically appears to make progress towards further increased empirical precision for the QGP shearviscosity elusive. Recent studies of higher harmonic eccentricity and flow coefficients [7] and theirfluctuations from collision to collision using event-by-event hydrodynamics provide, however, anovel angle that may allow to settle this question experimentally. This will be the main focus of mytalk.[1] Chun Shen, U. Heinz, P. Huovinen, H. Song, Phys. Rev. C82, 054904 (2010).[2] Chun Shen, U. Heinz, et al., “Radial and elliptic flow in Pb+Pb collisions at the Large HadronCollider from viscous hydrodynamics,” to be published.[3] H. Song, S. A. Bass, U. Heinz, T. Hirano and Chun Shen, arXiv:1011.2783.[4] H. Song, S. Bass and U. Heinz, Phys. Rev. C, in press [arXiv:1012.0555].[5] Chun Shen and U. Heinz, arXiv:1101.3703[6] H. Song, S. Bass, U. Heinz, T. Hirano and Chun Shen, arXiv:1101.4638 [nucl-th].[7] Zhi Qiu and U. Heinz, “Event-by-event shape and flow fluctuations in RHIC fireballs,” to be pub-lished.

Jets / 59

Jet shower evolution in medium and di-jet asymmetry in PbPbcollisions at the LHCAuthor: Guang-You Qin1

Co-author: Muller Berndt 1

1 Duke University


We study the evolution of a partonic jet shower propagating through a hot quark-gluon plasma. Adifferential equation is derived the evolution of the radiated gluon distribution as the jet propagatesthrough the medium. Combined with the in-medium evolution of the leading parton, we computethe depletion of the energy from the jet cone by dissipation through elastic collisions with mediumconstituents, by scattering of shower partons to larger angles, and by radiation outside the jet cone.Numerical results are presented for the nuclear modification of di-jet energy asymmetry in Pb+Pbcollisions at the LHC.

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Experimental study of quark and gluon jets in proton-proton andheavy-ion collisions.Author: Sona Pochybova1

1 KFKI Research Institute for Particle and Nuclear Physics-Hungari


We propose a set of jet-energy dependent cuts to be used to distinguish between quark and gluonjets experimentally based on a Monte-Carlo study of their properties. Using these cuts we are ableto achieve up to 80% purity of our selection. Further, we introduce the possibility to calibrate thesecuts via gamma-jet and multi-jet events, which represent clean production channels for quark andgluon jets, respectively. The calibration can happen on real data and thus, reduces the dependenceof the method performance on Monte-Carlo model predictions.We present the π, K and p spectra for quark and gluon jets in generated proton-proton and Pb-Pbcollisions at STAR and LHC energies.

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Simulations of thermodynamic andkinetic properties of the stronglycoupled quark-gluon plasmaAuthor: Vladimir Filinov1

Co-authors: Michael Bonitz 2; Pavel Levashov 1; Vladimir Fortov 1; Yurii Ivanov 3

1 Joint Institute for High Temperatures, Russian Academy of Sciences, Russia2 Institute for Theoretical Physics and Astrophysics, , Kiel, Germany3 GSI Helmholtzzentrum fur Schwerionenforschung GmbH,Darmstadt, Germany


In recent years, there has been an increasing interest in dynamics and thermodynamics of non-Abelian plasmas at both very high temperature and density. It is expected that a specific state ofmatter with unconfined quarks and gluons - the so called quark - gluon plasma (QGP) - can exist. Themost fundamental way to compute properties of the strongly interacting matter is provided by thelattice QCD. Interpretation of these very complicated computations requires application of variousQCD motivated, albeit schematic, models simulating various aspects of the full theory. Moreover,such models are needed in cases when the lattice QCD fails, e.g. at large baryon chemical potentialsand out of equilibrium. A semi-classical approximation, based on a point like quasi-particle picturehas been recently introduced in literature. It is expected that it allows to treat soft processes inthe QGP which are not accessible by the perturbative means and the main features of non-Abelianplasmas can be understood in simple semi-classical terms without the difficulties inherent to a fullquantum field theoretical analysis.Here we propose stochastic simulation of thermodynamics and kinetic properties for QGP in semi-classical approximation in the wide region of temperature, density and quasi-particles masses. Weextend previous classical nonrelativistic simulations based on a color Coulomb interaction to thequantum regime and take into account the Fermi (Bose) statistics of quarks (gluons) and quantumdegeneracy self-consistently.In grand canonical ensemble for finite and zero baryon chemical potential we use the direct quantumpath integral Monte Carlo method (PIMC) developed for finite temperature within Feynman formu-lation of quantum mechanics to do calculations of internal energy, pressure and pair correlationfunctions. The QGP quasi-particles representing dressed quarks, antiquarks and gluons interact viacolor quantum Kelbg pseudopotential rigorously derived in for Coulomb particles. This method hasbeen successfully applied to strongly coupled electrodynamic plasmas (EMP) . A strongly correlatedbehavior of the QGP is expected to show up in long-ranged spatial correlations of quarks and glu-ons which, in fact, may give rise to liquid-like and, possibly, solid-like structures. This expectation

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is based on a very similar behavior observed in electrodynamic plasmas.We have done already the first calculation of the QGP equation of state, spatial and color pair dis-tribution functions, diffusion coefficients and shear viscosity. The preliminary results has alreadybeen reported and discussed at the international conferences and meetings and are accepted forpublications.

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Direct jet reconstruction in d+Au collisions at PHENIXAuthor: Dennis Perepelitsa1

1 Columbia University

d+Au collisions at RHIC can be used to investigate cold nuclear matter effects on hard parton scatter-ing. d+Au collisions at different centrality (different N_coll) can probe nuclear parton distributions,initial state energy loss and final state parton interactions in the cold nucleus. They also providea valuable baseline for hard-scattering processes in heavy ion collisions. Measurements using jetreconstruction may provide a more sensitive probe of the parton level physics than inclusive single-particle measurements or two-particle correlations. We present the current results from direct jetreconstruction at PHENIX in d+Au collisions at sqrt(s) = 200 GeV. We discuss some of the challengesof direct jet reconstruction in a high-multiplicity heavy ion environment.

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Upsilon production at RHIC and LHCAuthor: Pengfei Zhuang1

Co-authors: Nu Xu 2; Yunpeng Liu 1

1 Tsinghua University2 China Center Normal University

CorrespondingAuthors: [email protected], [email protected], [email protected]

Upsilon production in heavy ion collisions at RHIC energy is investigated. While the transverse mo-mentum spectra of the ground state Upsilon(1s) are controlled by the initial state Cronin effect, theexcited (b b-bar) states are characterized by the competition between the cold and hot nuclear mattereffects and sensitive to the dissociation temperatures determined by the heavy quark potential. Weemphasize that it is necessary to measure the excited heavy quark states in order to extract the earlystage information in high energy nuclear collisions at RHIC.

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Non-extensive Statistical Approach to FragmentationAuthor: Karoly Uermoessy1

Co-authors: Gergely Gabor Barnafoldi 2; Tamas Sandor Biro 2

1 Dept. for Theor. Phys., ELTE; Research Institute for Particle and Nuclear Physics (KFKI)2 Research Institute for Particle and Nuclear Physics (KFKI)

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The first part of this talk presents a possible statistical physical description of hadron production inelectron-positron collisions. The main idea of the model is that hadrons produced inside a jet may beconsidered as a microcanonical ensemble, with multiplicity fluctuating event by event. The obtainedhadron spectrum is in good agreement with measured fragmentation functions [1].

Furthermore, at low energies, the above hadron spectrum coincides with the Tsallis distribution,which gives good fittings to hadron spectra stemming from proton-proton and nucleus-nucleus col-lisions. In the second part of the talk, I provide mathematical proof for the energence of the Tsallisdistribution in systems with special interactions, and present results of a parton collision cascadesimulation based on these interactions [2].

[1] Karoly Urmossy, Gergely Gabor Barnafoldi, Tamas Sandor Biro,Generalised Tsallis Statistics in Electron-Positron CollisionsarXiv:1101.3023 (Submitted to PLB)

[2] Karoly Urmossy, Tamas S. Biro, Gergely G. BarnaföldiPion Production Via Resonance Decay in a Non-extensive Quark-Gluon Medium with Non-additiveEnergy Composition RulearXiv:1101.3522 (Proceedings of Hot and Cold Baryonic Matter 2010)


Equilibration and Thermalization of Strongly Coupled Field The-oriesAuthor: Berndt Mueller1

Co-authors: Alice Bernamonti 2; Andreas Schaefer 3; Ben Craps 2; Esko Keski-Vakkuri 4; Jan de Boer 5; MasakiShigemori 6; Neil Copland 2; Vijay Balasubramanian 7; Wieland Staessens 2

1 Duke University2 Vrije Universiteit Brussel3 Universitaet Regensburg4 Helsinki Institute of Physics5 University of Amsterdam6 Nagoya University7 University of Pennsylvania


Using the AdS/CFT correspondence, we probe the scale-dependence of thermalization in stronglycoupled field theories following a quench, via calculations of 2-point functions, Wilson loops andentanglement entropy in 2, 3, and 4 dimensions. In the saddlepoint approximation these probesare computed in AdS space in terms of invariant geometric objects – geodesics, minimal surfacesand minimal volumes. Our calculations for two dimensional field theories are analytical. In ourstrongly coupled setting, all probes in all dimensions share certain universal features in their ther-malization: (1) a slight delay in the onset of thermalization, (2) an apparent non-analyticity at theendpoint of thermalization, (3) top-down thermalization where the UV thermalizes first. For homo-geneous initial conditions the entanglement entropy thermalizes slowest, and sets a time scale forequilibration that saturates a causality bound over the range of scales studied. The growth rate ofentanglement entropy density is nearly volume-independent for small volumes, but slows for largervolumes.

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Strong Coupled Pion SuperfluidAuthor: Yin Jiang1

Co-authors: Ke Ren 1; Pengfei Zhuang 1; Tao Xia 1

1 Tsinghua University


We calculate the meson screening mass and quark potential in a pionsuperfluid in the frame of Nambu–Jona-Lasinio model. The moststrong potential is always located at the critical point of pionsuperfluid along any of the axes of temperature and baryon andisospin chemical potentials. Unlike the temperature and baryondensity effect, the potential can not be efficiently suppressed inthe pion superfluid and the quark matter is always in a stronglycoupled phase even at extremely high isospin density.

Pre equilibrium and initial stage and global collective dynamics / 71

Bulk properties of PbPb collisions at the LHC measured by AL-ICE


Global variables, such as the charged particle multiplicity and the transverse energy are importantobservables to characterize Relativistic Heavy Ion collisions and to constrain model calculations.The charged-particle multiplicity dNch/deta(eta=0) and transverse energy dEt/deta(eta=0) are mea-sured at sqrt(s_NN)=2.76TeV in Pb-Pb collisions as a function of centrality and in p-p collisions. Thefraction of inelastic cross section seen by the ALICE detector is calculated either using a Glaubermodel or the data corrected by simulations of nuclear and EM processes, or data collected with aminimum bias interaction trigger. The centrality, defined by the number of nucleons participating inthe collision, is obtaine, via the Glauber model, by relating the multiplicity distributions of variousdetectors in the ALICE Central Barrel and their correlation with the spectator energy measured bythe Zero-Degree Calorimeters.The results are compared to corresponding results obtained at the significantly lower energies ofthe BNL AGS, the CERN SPS, and the BNL RHIC, and with models based on different mechanismsfor particle production in nuclear collisions. Particular emphasis will be given to a discussion onsystematic studies of the dependence of the centrality determination on the Glauber model, and thevalidity of the Glauber model at unprecedented collision energies.


Common discussion with 3 speakers


Global collective dynamics / 73

Anisotropic flow from ALICE

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We report on the measurements of anisotropic flowwith the ALICE detector at the LHC. For chargedparticles we present the first triangular, quadrangular and pentagonal flow measurements. The flowof charged and identified particles is compared to hydrodynamic model predictions at low-p_t andfor identified particles at intermediate-p_t the so-called number of constituent quark scaling is in-vestigated. At higher transverse momentum we compare the elliptic flow results with expectationfrom parton energy loss.For the integrated elliptic flow we show the scaling with the initial eccentricity and we quantify themagnitude of the event by event fluctuations.These results indicate strong collective flow and are consistent with expectations for the created hotand dense system created at the LHC.


Flow measurements from the CMS experimentCorresponding Author: [email protected]

We report on the CMS measurements of charged hadron anisotropic azimuthaldistributions from PbPb collisions at √sNN= 2.76 TeV and theirdecomposition into a Fourier series up to the 6th coefficient. The results arepresented as a function of transverse momentum, centrality and pseudorapidityand cover a broad kinematic range. The relation between the different harmoniccoefficients and the scaling with the respective participant eccentricity arestudied. These results could provide constraints on the theoretical descriptionof the early dynamics in the hot and dense medium and its transport properties.

Hard probes I: hadron spectra / 75

Quenching of single hadron and photon spectra from RHIC toLHCCorresponding Author: [email protected]

I will discuss the generic features of parton energy loss effects on the quenching of large-pT hadrons,as well as more quantitative studies. The differences expected from RHIC to LHCwill be highlighted.The quenching of prompt photons will also be discussed in detail. Finally, I will stress the need forprecise baseline measurements of hadrons and photons in pp and pPb collisions.


Particle production at large transverse momentum with ALICE


We present transverse momentum distributions of charged particles and identified hadrons in ppand Pb-Pb collisions, measured by ALICE at the LHC. The Pb-Pb data are presented in intervals ofthe collision centrality and cover transverse momenta up to 50 GeV/c. Nuclear medium effects are

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studied in terms of the nuclear modification factor R_AA. The results indicate strong suppression ofhigh-p_T particles in Pb-Pb collisions, consistent with a large energy loss of hard-scattered partonsin the hot, dense, and long-lived medium created at the LHC.

Hard probes II: true jets / 77

Monte Carlo tools for jet quenching



STAR on reconstructed jets and jet-like correlations


Heavy flavor and Quarkonia in medium / 79

Applying the AdS/CFT correspondence to non-abelian plasmas



PHENIX heavy flavor


Quarkoniameasurements by theCMS experiment in pp andPbPbcollisions


CMS is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicityenvironment of nucleus-nucleus collisions. Such probes areespecially relevant for studying the quark gluon plasma since they are producedat early times and propagate through the medium, mapping its evolution.Quarkonia and bottomonia are sensitive to the evolution of the medium. Inparticular, the Jψ production in heavy ion collisions has been studied atdifferent energies and with different collision systems without yet giving aglobal picture that is fully understood. Measuring the charmonium production atthe LHC energies in PbPb collisions will help constraining predictions, inparticular those expecting high recombination of prompt J/Psi or

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suppression in hot medium. We will review CMS J/Psi measurements in ppcollisions at √sNN=7~TeV, which allow precision studies of quarkoniaproduction and serve as a reference for the observation of hot nuclear effects.CMS is able to distinguish non-prompt J/psi from prompt J/psi in PbPbcollisions, and will present the prompt J/psi production cross-section inPbPb inclusively and as a function of transverse momentum, rapidity and numberof nucleons participating in the collision. Finally, we compare the B fractionmeasured in PbPb collisions with that measured in pp at various energies. TheLHC centre-of-mass energy allows copious Y production in PbPbcollisions. Detailed measurements of bottomonium will help characterize thedense matter produced in heavy-ion collisions beyond what was accessible atRHIC (mostly) with charmonia. The full spectroscopy of quarkonium states hasbeen suggested as a possible thermometer for the QGP. With its excellent dimuon mass resolution,CMS has measured the three Y states in pp collisions.With the 2010 PbPb data sample, CMS has observed the Y(1S) as well asexcited states. The Υ(1S) cross-section is presented as a function oftransverse momentum, rapidity and centrality, and excited state. Suppression ofthe excited state in PbPb will be discussed.

82

Theory

Electromagnetic probes

83

Experiments

Photons and dileptons

84

Theory

AdS/CFT, more

85

Theory

Lattice QCD

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86

Experiments

Hadrochemistry

Correlations & fluctuations / 87

Correlations and fluctuations from lattice QCDCorresponding Author: [email protected]

88

p + A

89

New challenges at the low energy frontier

SPS, FAIR, low energy RHIC, NICA/MPD (experiments and theory)

90

e + A

New challenges / 91

The high energy frontier of A-ACorresponding Author: [email protected]


Non-conformal holography of light and heavy quark jet quench-ing at RHIC and LHCAuthor: Andrej Ficnar1

Co-authors: Jorge Noronha 2; Miklos Gyulassy 1

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1 Columbia University, New York, USA2 Universidade de Sao Paulo, Sao Paulo, Brazil


We investigate the connection between the conformal anomaly in the confinement transition regionand quenching of heavy and light quarks in heavy ion collisions at RHIC and LHC by using a newnon-conformal holographic model with a dilaton field. Holographic thermodynamic properties ofthe sQGP are constrained by lattice QCD calculations. The string drag force model of jets is gen-eralized to include both trailing and falling string scenarios. We compare the differential nuclearmodification of light and heavy quark jets predicted by this model emphasizing the novel quarkmass and energy dependence through the confinement transition region.

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JetModificationViaTheLPMEffect In InfiniteQuarkMatterAuthor: Christopher Coleman-Smith1

1 Duke Physics


Recent results for Pb+Pb collisions at √sNN = 2.76~TeV fromthe LHC have shown dramatic di-jet asymmetry, implying a strong medium modification of jets asthey pass through the QGP.A fully-relativistic Monte-Carlo Boltzmann transport code, the PartonCascade Model (PCM), is used to simulate the development of a jet in apartonic medium. The PCM includes collisional and radiative processesand a local probabilistic implementation of theLandau-Pomeranchuck-Migdal (LPM) effect.The PCM is particularly suitable for the examination of jet modification as it treats both medium andjet partons on an equal footing, allowing for full tracking of the process.We present the first infinite matter results, including an accuratetreatment of the LPM effect, for the energy flow within the jet conealongside results for the rate at which energy lost from the jet isdeposited back into the medium. We also apply our simulation to theobserved ATLAS dijet asymmetry.

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Measuring parton energy loss at RHICAuthor: Michael Tannenbaum1

1 Brookhaven National Laboratory (BNL)-Unknown-Unknown


The method of measuring xh, the ratio of pTa, the away-parton pT , to pTt, the trigger-parton pT ,using two-particle correlations at RHIC, which is sensitive to the away parton energy loss due to thesurface bias, will be reviewed. This measurement is simply related to the new variable introducedat LHC for the di-jet transverse momentum imbalance, AJ = (pTt − pTa)/(pTt + pTa) = (1 −xh)/(1 + xh). Results from two-particle correlations at RHIC for xh = (1− AJ)/(1 + AJ) will bereviewed and new results will be presented and compared to LHC measurements using jets.

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Dynamical magnetic effects and the nonphotonic electron puzzleat RHICAuthor: Alessandro Buzzatti1

Co-author: Miklos Gyulassy 1



Perturbative magnetic scattering effects in the HTL approximation predict enhanced jet energy lossfor both light and heavy quarks. Whereas this helps to reduce the discrepancy of pQCD tomographywith single electron data at RHIC, the new computations reveal significant disagreement with pionquenching data due to overestimation of the quenching suffered by light jets. We discuss whetherthis is sufficient to rule out the HTL approximation of the QGP medium. The role of future flavortagged charm and bottom jet observables at RHIC and LHC is emphasized.

Overviews / 96

Overview of the experimental results by the ALICE Collabora-tion


In this talk we summarize the results obtained by ALICE Collaboration in the first Pb-Pb run atLHC.

Overviews / 97

Results from lead-lead collisions with the ATLAS Detector at theLHC


Overviews / 98

Overview of the experimental results by the CMS Collaboration


We will present early results of the CMS experiment from PbPb collisions at√sNN = 2.76 TeV, probing quark and gluon matter at unprecedentedvalues of energy density. The capabilities of the CMS apparatus allows us toinvestigate various hard probes, as well as bulk particle production andcollective phenomena, using the calorimetry, muon and tracking systems coveringa large range in pseudorapidity, complemented by a flexible two-level triggersystem.

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Overviews / 99

PHENIX Highlights


After establishing the creation of dense partonic matter in the earlyyears of RHIC, the focus of recent experimental and theoretical efforthas been to determine the properties of this partonic medium. Withthe advent of the LHC, there is now a new aspect to this quest:are the properties of the medium created at the LHC different from thatcreated at RHIC? In this light, we willpresent the latest experimental results of the PHENIX collaboration,further constraining the properties of the sQGP at RHIC.

Overviews / 100

STAR highlights


101

Opening

Overviews / 102

LHC accelerator


Overviews / 103

Theory overview


Student lectures / 104

Heavy-ion collisions and QCD: the big picture


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Soft physics and hydrodynamics



Jets, high-pT hadrons and prompt photons



Heavy-quarks and quarkonia


Famous plot session / 108

Initial conditions, low-x QCD, thermalization

Corresponding Author: david.d’[email protected]


QCD phase transition, hydrodynamics, hadronization



Jets, high-pT hadrons, and prompt photons


Heavy-quarks and quarkonia


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Jets / 112

Medium induced collinear radiation from soft collinear effectivetheory (SCET)Authors: Francesco D’Eramo1; Hong Liu1; Krishna Rajagopal1

1 MIT

The propagation of hard partons through the strongly interacting matter created in high energyheavy-ion collisions involves widely separated scales. The methods of Effective Field Theories (EFT)can provide a factorized description at lowest nontrivial order, and a formalism where the correctionto this factorization are calculable systematically order by order in the small ratios between thedifferent scales. In this talk I will present our recent results on the calculation of the spectrum ofthe gluons emitted by the hard parton, where the radiated gluons are collinear with the incominghard parton and with arbitrary energy (not necessarily much softer than the energy of the hardparton). I will also briefly discuss how to extend the analysis to include the emission of gluonscollinear in arbitrary directions and gluons with all the components of their momentum scalingas the medium characteristic energy scale (soft gluons). In particular I will show how powerfulconcepts like collinear gauge invariance and reparameterization invariance simplify the derivationof the effective Lagrangian.

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Suppression of the repulsive force in nuclear interactions nearthe chiral phase transitionAuthor: Chihiro Sasaki1

Co-authors: Hyun Kyu Lee 2; Mannque Rho 3; Won-Gi Paeng 2

1 Frankfurt Institute for Advanced Studies2 Hanyang University3 CEA Saclay


One of the issues in hot/dense QCD is to understand the stateof matter in the vicinity of phase transition from hadronicmatter to quark matter expected to be created in heavy-ion collisions, or to be present in the interiorof compact stars.In nuclear physics, a scalar meson plays an essential role asknown from Walecka model that works fairly well for phenomenanear nuclear matter density. On the other hand, at high density, the relevant Lagrangian that hascorrect symmetry is the linear sigma model, and the scalar needed there is the sigma that is thefourth component of the chiral four-vector. Thus in order toprobe highly hot/dense matter, we have to figure out how thechiral scalar at low temperature/density transmutes to the fourth component of the four-vector.

In this talk, we introduce a chiral scalar as a dilaton associatedwith broken conformal symmetry and responsible for the trace anomaly of QCD and discuss theproperties of nuclear matter athigh density [1]. As the “dilaton limit” is taken, which drives a system from nuclear matter densityto near chiral restoration density, a linear sigma model emerges from the highly nonlinearstructure with the omega meson decoupling from the nucleons.A striking prediction of this procedure is that as the dilaton limit is approached as density increases,the omega-nucleon interaction known to be repulsive at low density gets strongly suppressed athigh density. The omega-mediated short-range repulsion gets also suppressed. This occurs in the

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rho-meson exchanged repulsion too. Consequently the symmetry energy which plays a crucial rolein the structure of compact stars gets suppressed. An immediate consequence would be that theequationof state (EoS) of dense matter will be softened at high densityand would accommodate the EoS without any exotica consistent with the recent measurement of a2-solar-mass neutron star.

Reference:[1] Chihiro Sasaki, Hyun Kyu Lee, Won-Gi Paeng and Mannque Rho,“Conformal anomaly and the vector coupling in dense matter,”arXiv:1103.0184 [hep-ph].

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Equation of state of a strongly-interacting QGP and charmoniumsuppressionAuthor: binoy patra1

Co-author: Vineet Agotiya 1

1 Indian Institute of Technology Roorkee


Recently we have developed the equation of state for a strongly interacting quark-gluon plasma inthe framework of strongly-coupled QED plasma by incorporating the non-perturbative effects interms of nonzero string tension in the deconfined plasma phase,unlike the Coulomb interactions alone.Our results on thermodynamic observables\em viz. pressure, energy density, speed of sound etc. nicelyfit with the lattice equation of state for gluon, massless and aswell \em massive flavored plasma. Motivated by this agreement withlattice results, we have employed our equation of state to estimate thequarkonium suppression in an expanding, dissipative strongly interactingQGP produced in relativistic heavy-ion collisions and our predictionmatches exactly with the recent PHENIX data on the centralitydependence of J/ψ suppression in Au+Au collisions at BNL RHIC.We have also predicted for the Υsuppression in Pb+Pb collisions at LHC energywhich could be tested cleanly in the ALICE experiments at CERN LHC.

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First-principles derivation of the jet energy-momentum deposi-tion source term in the QGP and its implications for shockwaveformation at RHIC and at the LHCAuthor: Richard Neufeld1

1 LANL


I present a new derivation for the distribution of energy and momentum transmitted from a fastparton to a medium of thermalized quarks and gluons, or the source term. A thermal field theoryapproach enables the direct evaluation of the source term from the divergence of the QCD energy

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momentum tensor. This approach is more general than previously used Boltzmann transport tech-niques and allows for the coupling of realistic external quark and gluon currents to the Lagrangianof soft QCD matter. Specifically, I consider for the first time the medium response to back-to-backjets and jets + medium-induced gluon bremsstrahlung. The calculation includes the effects of quan-tum interference between the interactions of the multiple fast partons with the medium, and demon-strates that the energy absorbed by the medium is enhanced in a non-trivial way due to the presenceand formation time of medium induced radiation. The numerical results suggest that the use of suchrealistic external currents has important implications for the shockwave formation in relativisticheavy ion collisions at RHIC and the LHC and soft-to-intermediate transverse momentum particlecorrelation phenomenology.

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Momentum dependence of quarkonium production at RHIC andLHCAuthor: Yunpeng Liu1

Co-authors: Nu Xu 2; Pengfei Zhuang 1

1 Tsinghua University2 CCNU (Central China Normal University)


The momentum dependence of quarkonium dissociation temperature in hot medium is investigatedand is applied to the quarkonium suppression in high energy nuclear collisions. For a fast movingquarkonium, the screening is significantly weaken, its dissociation temperature becomes higher andleads to a transverse momentum broadening in heavy ion collisions at RHIC and LHC.

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Strong color fields effects and baryon/meson anomaly in p+p andcentral Pb+Pb collisions at L H C energies(*).Author: VASILE TOPOR POP1

Co-authors: Charles Gale 1; Jean Barrette 2; Miklos Gyulassy 3

1 McGill University, Montreal, Canada2 McGILL UNIVERSITY, MONTREAL, CANADA3 Columbia University, New York, USA


With the HIJING/BBar v2.0 event generator, we explore the phenomenological consequences ofthe suppression of perturbative quantum chromo-dynamics (pQCD) mini-jet production and of en-hanced “in medium” strong longitudinal color field. Nuclear effects like shadowing and parton en-ergy loss (”jet quenching”) are included.This analysis focuses on p+p collisions at centre of mass energy(sqrt(sNN)) 0.900, 2.36 and 7 TeV, andon central Pb+Pb collisions at sqrt(sNN) = 2.76 TeV, where recent datahave been reported by LHC Collaborations (ALICE, ATLAS, CMS).The effective energy-dependent string tension values are constrained by p+p data from RelativisticHeavy Ion Collider (RHIC), the Tevatron, and recent Large Hadron Collider (LHC) runs. The pQCD

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cut-off value p0(s) is constrained byAu+Au collisions data fromRHIC. Data on charged hadronmulti-plicity and charged hadron nuclear modification factor (RAA) in central (0-5%) Pb+Pb collisions fromthe ALICE experiment at the LHC are used to constrain the main parameters of the “jet quenching”phenomena (energy loss and mean free path of initial parton-parton interactions). Predictions forthe energy and centrality dependence of rapidity densities (2dNch/dy/Npart) and the hadron flavordependence(mesons and baryons) of the nuclear modification factor RAA are presented. By study-ing baryon/meson ratios, we show that the jet quenching in central collisions suppresses the hardpQCD component of the particle spectra, thereby exposing a novel component of baryon dynamicsthat we attribute to (gluonic) baryon-anti-baryon junctions (JJbar). We predict that a baryon/mesonsanomaly at intermediate transverse momentum values will persist at LHC energies, with a moderatecentrality dependence.

(*) This work is being supported by NSERC (Canada) and by theUS Department of Energy.

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An effective theory for jet propagation in dense QCD matter: jetbroadening, radiative energy loss and LHC phenomenologyAuthor: grigory ovanesyan1

1 LANL


Soft Collinear Effective Theory (SCET) is a powerful tool tostudy jet physics. In order to describe jet propagation in the denseQCD matter created in ultra-relativistic nuclear collisions, SCETneeds to be modified by the inclusion of the transverse to the jetaxis gluon mode, which is commonly referred to as a Glauber gluon. Weconstruct the Lagrangian of the resulting effective theory anddemonstrate the gauge invariance of the jet broadening and radiativeenergy loss results. We show how using effective theory methods allowsus to go beyond the soft gluon approximation, which is commonly usedin the heavy-ion energy loss phenomenology. Our results are presentedfor realistic jet-medium scattering cross sections with fully dynamicQGP response. Finally, we discuss the implications of thenewly-developed theory for LHC hard probes phenomenology with anemphasis on the quenching of leading particles and jets.

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Directed Flow in event-by-event hydrodynamicsAuthor: Fernando Gardim1

Co-authors: Frederique Grassi 1; Jean-Yves Ollitrault 2; Matthew Luzum 2; Yogiro Hama 1

1 USP2 Saclay


Fluctuations in the initial geometry of a nucleus-nucleuscollision have been recently shown to produce the correlationstructures known as ridge” andshoulder”. These event-by-event

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fluctuations result in new types of anisotropic flow, such astriangular flow v3 and a new type of directed flow v1,which, unlike the usual directed flow, is also present atmidrapidity. The anisotropic flows due to the fluctuations in theinitial density profile result in different reference anglesΨn for every harmonic n, which are not necessarilycorrelated with the event plane angle Ψ2 (the elliptic flowreference angle), used by the experimentalists to measure theanisotropic flows, as v1, v2 and v4. Unlike triangularflow, this new v1 has not been studied in a hydrodynamicframework.

This work is based on the first quantitative predictions for thisnew v1 in Au-Au collisions at the top RHIC energy, using thehydrodynamic code NEXSPheRIO. NEXSPheRIO solves the relativisticideal hydrodynamics using initial conditions provided by the eventgenerator NeXus, providing good description for severalobservables, like elliptic flow. Shear viscosity is notimplemented in this computation, though its effect should besmaller than higher harmonics, for instance v2.

First, we compute this new v1 versus transverse momentum andcentrality for Au-Au collisions at RHIC using the hydrodynamiccode NeXSPheRIO. Even without dedicated analysis of this newv1, indirect evidence has been obtained from recent STARcorrelation data, and we compared our results with those inferreddata, finding remarkable agreement.

As the fluctuations in the initial geometry break the symmetry ofthe initial density profile, there will be one direction where theprofile is steepest. This effect can be quantified by themagnitude dipole asymmetry ε1, and by the steepestdirection for a smooth profile Φ1. For smooth initialconditions, one expects Ψ1 = Φ1 and v1 ∝ ε1 in each event. We compute those features for ourbumpy initial conditions and compare with the directed flowquantities. We find that the event plane of v1 is correlatedwith the angle of the initial dipole of the distribution, aspredicted, though with a large dispersion, but it is uncorrelatedwith the reaction plane. This shows that the dipole asymmetry isindeed the mechanism to create v1.

Reference: arXiv:1103.4605

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SiliconTracking for theCompressedBaryonicMatter Experimentat FAIRAuthor: Johann Heuser1

1 GSI Helmholtz Center for Heavy Ion Research GmbH, Darmstadt, Germany


The Compressed Baryonic Matter (CBM) experiment at the international Facility for Antiprotonand Ion Research (FAIR) will conduct a comprehensive research programme on nuclear matter athigh net baryonic densities. The fixed-target detector will record hadronic, leptonic and photonicobservables from proton-nucleus and nucleus-nucleus collisions. Many of them are rare so that highcollision rates up to 10 MHz will have to be mastered at minimum bias. The central component is asilicon tracking system for the trajectory and momentum determination of the hundreds of charged

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particles created in the collisions. Their efficient reconstruction is prerequisite for essentially all CBMobservables. The tracker will comprise radiation hard siliconmicrostrip detectors and self-triggeringreadout electronics assembled into a large-area low-mass system. Progress with the design of thesystem, the assessment of its expected performance, and the realization of prototype componentswill be reported.

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Directed flow and early thermalizationAuthor: Iwona Wyskiel-Piekarska1

Co-author: Piotr Bozek 1

1 Institute of Nuclear Physics PAN


For the first time, the generation of the directed flow of particles emitted from the fireball created inheavy-ion collisions at RHIC is described using a 3+1D hydrodynamical model. The initial fireballdensity is constructed as a sum of contributions from forward and backward going participants. Thisasymmetry in theemission from the individual participants leads to a tilt of the source. Our model reproduces theexperimentally observed negative directed flow in a wide range of central pseudorapidities and re-produces correctly the scaling of the directed flow when going from Au-Au to Cu-Cu systems [1].We also propose to measure the thermalization time in the early stage of heavy-ion collisions usingthe directed flow of particles. We show that the directed flowis a very sensitive measure of the pressure equilibration in the first fm/c of the evolution. We demon-strate in hydrodynamic calculations that the directed flow is strongly reduced in the presence ofeven a very short pressure anisotropy. Our calculations show that the system must thermalize fast(<0.25fm/c). This suggests that the matter behaves as a strongly coupled system already at the firststages [2].

[1] P. Bozek and I. Wyskiel, Directed flow in ultrarelativistic heavy-ion collisions, Phys. Rev. C 81054902 (2010)[2] P. Bozek and I. Wyskiel-Piekarska, Indications of early thermalization in relativistic heavy-ioncollisions, Phys. Rev. C 83 024910 (2011)

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What is the surface tension of quark gluon bags?Authors: Gennady Zinovjev1; Kyrylo Bugaiev1

1 Bogolyubov Inst. for Theor. Phys. (ITP), Kiev, Ukraine


We discuss the novel view at the colour confinement which,on the one hand, allows us to find out the surface tension coefficientof quark gluon bags and, under a plausible assumption, to determine the endpoint temperature ofthe QCD phase diagram, on the other hand.The developed model considers the confining colour tube as the cylindricalquark gluon bag with non-zero surface tension.A close inspection of the free energies of elongated cylindrical bag and the confining colour tubethat connects the static quark-antiquark pairallows us to find out the string tension in terms of the surface tension, thermal pressure and the bagradius. Using the derived relation it is possible

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to estimate the bag surface tension at zero temperature directly from the lattice QCD data. The re-quirement of positive entropy density of such bags leads tonegative values of the surface tension coefficient of quark gluon bags at the cross-over region, i.e. atthe continuous transition to deconfined quarks and gluons.It is shown that such an approach naturally accounts for an existence of a very pronounced surpris-ing maximum of the string entropy observed in the lattice QCD simulations, which, as we argue,signals about the fractional surface formation ofthe confining tube. Also we analyze the vicinity of the (tri)critical endpoint of the QCD phase dia-gram and discuss the role of vanishing surface tension coefficient for the endpoint existence.

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DENSE COLD MATTER STUDY WITH SPECIAL TRIGGER ATTWA, NUCLOTRON, NICA AND FAIR. Project Status.Author: Alexey Stavinskiy1

1 ITEP


New phase diagram sector at extrimely large baryon density and low temperature is proposed forthe laboratory study at TWA(ITEP),Nuclotron-M,MPD-NICA(JINR), CBM@SIS100(FAIR). High ptcentral rapidity double cumulative trigger for this study is proposed and tested experimentally atITEP ion accelerator by FLINT collaboration.FLINT experiment is dedicated to the research programof dense cold matter search and study. Experimental data of two runs (2007 and 2010) are presented.Photons spectrawheremeasured in CBe interaction at 3.2GeV/nucleonwithin angular region 35°–70°(l.s.). It is shown, that the measured photon spectra are indicating the domination of flucton-fluctoninteraction. Results of two runs are consistent with each other. Proposed measurements programsfor future facilities MPD-NICA and CBM-FAIR(SIS100) are discussed.

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Enhancement of flow anisotropies due to magnetic field in rela-tivistic heavy-ion collisionsAuthor: Saumia Pandiat1

Co-authors: Ajit Srivastava 2; Ranjita Mohapatra 2

1 Institute of Physics2 Institute of Physics


It is known that the presence of background magnetic field in cosmicplasma distorts the acoustic peaks in CMBR. This primarily results from different types of waves inthe plasma with velocitiesdepending on the angle between the magnetic field and the wave vector. We consider the conse-quences of these effects in relativistic heavy-ion collisions where very strong magnetic fields ariseduring early stages of the plasma evolution. We show that flow coefficients can be significantly af-fected by these effects when the magnetic field remains strong during early stages due to stronginduced fields in the conducting plasma. In particular, the presence of magnetic field can lead toenhancement in the elliptic flow coefficient v_2.

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Pre-equilibrium and initial state / 131

Initial state fluctuations at RHIC and LHC: hadronic or partonicorigin?Author: Hannah Petersen1

Co-authors: Berndt Mueller 1; Steffen Bass 1

1 Duke University

This talk will discuss how triangular flow measurements in Pb+Pb collisions atthe LHC can be used to constrain the origin of initial state fluctuations. Weexplore the energy dependence of elliptic and triangular flow within a(3+1)-dimensional hybrid framework starting from a non-equilibrium initial statewith event-by-event fluctuations and including an ideal hydrodynamical expansionphase followed by hadronic Boltzmann transport. This approach has been shown todescribe well the existing RHIC and LHC data on bulk observables such asparticle yields, spectra and elliptic flow. The initial energy deposition can bemodeled either in a partonic or a hadronic picture using, respectively, a partoncascade or the hadronic transport model UrQMD. We present adetailed comparison between the shape and fluctuations of the two initialconditions prior to the hydrodynamical evolution. Our analysis then compares thedifferences in final state observables such as triangular flow in order toidentify sensitivities to the degrees of freedom driving the energy deposition.

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Centrality dependence of observables in the core - corona model

Author: Joerg Aichelin1

Co-authors: Constantin Schreiber 1; Klaus Werner 1

1 subatech


To understand the centrality dependence of the measured observables, like the multiplicity < pt >and the elliptic flow of identified particles at midrapidity as well as the elliptic flow of chargeshadrons, has been a challenge for theory since many years. Although the multiplicity of differentparticles in central collisions corresponds exactly to the expectation for a completely thermalizedsource the centrality dependence is incompatible with this assumption.

Awhile ago it has been realized that even in themost central collisions there remain particles (usuallyclose to the surface of the interaction zone) which do not come to equilibrium (corona particles)whereas others come to a local equilibrium (core particles). Corona particles produce hadrons likepp collision. The relative fraction of corona particles can be calculated in the Glauber approachand increases with decreasing centrality? This variable core fraction is the origin of the centralitydependence of the observables.

The approach has no free parameter and reproduces quantitatively the experimental results. Espe-cially it explains an observations which have been unexplained since quite a while: the enhancementof (multi) strange baryons and the fact that this enhancement becomes smaller at larger beam ener-gies.

Recently this model has been extended to dynamical variables like the centrality dependence of< pt > and v2 of identified particles. Themodel reproduces quantitatively the centrality dependenceof the elliptic flow of charged particles

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without any new parameter which has been considered so far as an observable which allows to fixthe viscosity of a plasma. Our model shows that this centrality dependence can also be predictedassuming the same fraction of completely equilibrized core and not equilibrized corona particleswhich has been used to understand the centrality dependence of the multiplicity.

In the presentation we will display the model and make comparisons with the EPOS event genera-tor which is based as well on the distinction between core and corona particles and describes therapidity dependence of many observables. Then we demonstrate that the centrality dependence ofall observables at midrapidity is well described in this approach, at SPS as at RHIC, and for CuCu aswell as for AuAu. If data are available we will extend the model to LHC energies.The interpretation of the results in physical terms concludes the presentation.

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The realistic QCD equation of state in relativistic heavy-ion colli-sions and the early UniverseAuthor: Wojciech Florkowski1

1 Institute of nuclear Physics, Krakow


The realistic equation of state of strongly interacting matter [1,2], that has been successfully appliedin the recent hydrodynamic studies of hadron production in relativistic heavy-ion collisions at RHIC[3,4], is used in the Friedmann equation to determine the precise time evolution of thermodynamicparameters in the early Universe [5]. A comparison with the results obtained with simple ideal-gas equations of state is made. The realistic equation of state describes a crossover rather than thefirst-order phase transition between the quark-gluon plasma and hadronic matter. The numericalcalculations show that small inhomogeneities of strongly interacting matter in the early Universeare moderately damped during such crossover.

The crossover character of the QCD transition indicates that there are small chances for observationof exotic phenomena connected with the first order phase transitions (quark nuggets, strangelets).Similarly, damping of the energy density perturbations suggests that no strong energy-density peaksare formed, that may lead to the formation of cold dark matter clumps discussed in earlier publica-tions.

[1] Y. Aoki, Z. Fodor, S. D. Katz, K. K. Szabo, JHEP01, 2006, 089.

[2] S. Borsanyi et al., JHEP09, 2010, 073.

[3] M. Chojnacki, W. Florkowski, Acta Phys. Polon.B38, 2007, 3249.

[4] W. Broniowski, M. Chojnacki, W. Florkowski, A. Kisiel, Phys.Rev.Lett.101, 2008, 022301.

[5] W. Florkowski, Nucl.Phys.A853, 2011, 173.

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Role of Finite Size Baryons in QCD Phase Transition and CriticalPointAuthor: Prashant Kumar Srivastava1

Co-author: C. P. Singh 1

1 Banaras Hindu University

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The physics regarding the existence of the critical point on the QCD phase boundary still remainsunclear and its precise location is quite uncertain. We follow the suggestion of T. D. Lee et. al.[Phys. Rev. D9, 2291 (1974)] that a phase transition at high baryon density in a bulk matter can berealized in which nucleon loses part of its mass and thus baryons play a significant role in the phasetransition. We suggest that the hadron gas consists of pointlike mesons and each baryon having ageometrical hard-core size. It means that mesons can fuse into one another while baryons experiencea repulsive force with other baryons when densely packed. We formulate an excluded volumemodelexisting for the equation of state (EOS) of hot, dense hadron gas and for the quark gluon plasma weuse a thermodynamically consistent quasiparticle model (QPM). We construct a first order phasetransition using Gibbs’ equilibrium criteria. This leads to an interesting and surprising finding thata critical point exists in such a formulation beyond which a cross-over region appears. We find thatsuch a picture always appears in all excluded volume models considered in the literature. For idealhadron gas model, there is no critical point in the diagram. In the mean field model also, we do notget a critical point unless we incorporate an excluded potential effect. Our analysis strongly suggeststhat the existence of a critical point and a cross-over region owes its explanation in the finite sizebaryons in the hadron gas. We find an interesting result that the ratio of the baryons to the totalhadrons at the critical point is around 0.2 in all types of models and thus a cross-over region startsas soon as this ratio becomes smaller than 0.2.


Far-from-equilibrium anisotropic collective flowAuthor: Nicolas Borghini1

Co-author: Clément Gombeaud 1



Novel analytical results for the anisotropic collective flow of massive particles with a small interac-tion cross-section are presented. In particular, we show that, even when particles rescatter at mostonce, a sizable elliptic flow v2 is generated, withmass ordering of the various particle species.

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Describing sQGP through the Friedberg-Lee modelAuthor: Song Shu1

Co-author: Jiarong Li 2

1 Faculty of Physics and Electronic Technology, Hubei University, China2 Institute of Particle Physics, Hua-Zhong Normal University, China


The FL model is studied at finite temperature and density. Thesoliton solutions of the FL model in deconfinement phasetransition are solved and thoroughly discussed for certainboundary conditions. We indicate that the solitons before andafter the deconfinement have different physical meanings: thesoliton before deconfinement represents hadron, while the solitonafter the deconfinement represents the bound state of quarks whichleads to a sQGP phase. The corresponding phase diagram is given.

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Jets / 140

Measurements of Jets and Jet Quenching in sqrt(s_NN)=2.76 TeVPbPb Collisions with the ATLAS Detector at the LHCAuthor: Toni Baroncelli1

1 Physics Department University of ROMA TRE - Rome -Italy


Jet quenching, the parton energy loss in the hot and dense medium created in ultra-relativisticheavy ion collisions, is a well-established experimental phenomenon at RHIC. However, existingsingle hadron, di-hadron and multi-hadron measurements from RHIC do not provide a completeunderstanding of the experimental results and do not sufficiently constrain theoretical models. Re-constructed jet measurements in heavy ion collisions are expected to significantly improve exper-imental sensitivity to quenching and to more stringently constrain theoretical descriptions of thequark/gluon-medium interaction. Thus, prior to its commencement, it was anticipated that the LHCheavy ion program would substantially advance the study of jet quenching by providing access tojets with transverse energies in excess of 100 GeV – sufficiently high that the underlying eventwould provide only a modest perturbation to the jet measurements. Immediately following turn-onof the LHC in November, 2010, that expectation was satisfied through the observation of large di-jetasymmetries that may indicate substantial jet quenching. In this talk we will present results fromATLAS measurements of single jet production, di-jet correlations and jet fragmentation in Pb+Pbcollisions at

√sNN = 2.76~TeV. These results include an update on the original di-jet asymmetry

analysis using the full statistics from the Fall 2010 LHC Pb+Pb run.


Measurement of elliptic flow in sqrt(s_NN)=2.76 TeV PbPb colli-sions with the ATLAS detector at the LHC.Author: Toni Baroncelli1



The measurement of the elliptic flow for charged particles in Pb+Pb collisions at sqrt(s_NN)=2.76TeV with the ATLAS detector will be presented in a wide range of pseudorapidity, transverse mo-mentum and collision centrality. The elliptic flow is measured by correlating azimuthal angles ofreconstructed particle tracks with the event plane angle obtained from forward calorimeters. Alarge pseudorapidity gap between the tracking system and forward calorimeters significantly re-duces contributions from short-range non-flow effects. For the first time at this energy, elliptic flowis measured over 5 units of pseudorapidity, from -2.5 to 2.5, and over a broad range in transversemomentum, 0.5-20 GeV. The results will be discussed in the context of previous measurements andtheoretical model predictions.


Measurement of charged particle pseudorapidity density in PbPbcollisions at sqrt(s_NN) = 2.76 TeVwith the ATLAS detector at theLHCAuthor: Toni Baroncelli1

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Charged particle multiplicity is an important bulk observable for heavy ion collisions. It measuresthe global features of themedium produced and constrains the initial conditions of the system. It alsoprovides an important test for dynamical model calculations which predict the dependence of multi-plicity on centrality at RHIC and the LHC. We present the study of charged particle pseudorapiditydensity distributions over a broad range of pseudorapidity and centrality in Pb+Pb collisions at √sNN= 2.76 TeV with the ATLAS detector at LHC. The centrality dependence of the particle density nearmid-rapidity scaled by the number of participating nucleon pairs (dNch/dη(|η| < 0.5)/(0.5Npart)) ispresented. Comparisons with results from previous measurements are used to study the collision en-ergy dependence. The pseudorapidity distributions measured over four units of pseudorapidity arecomparedwith those of different collision systems and energies as well as dynamical models.

Jets / 144

Measurements of chargedparticle spectra in sqrt(s_NN)=2.76 PbPbcollisions with the ATLAS detector at the LHCAuthor: Toni Baroncelli1



The measurement of charged particle spectra in heavy ion collisions is a direct way to study proper-ties of hot and dense matter created in these interactions. The centrality dependence of the spectralshape is an important tool to understand the interplay between collective flow and energy loss mech-anisms. The ATLAS detector at the LHC took lead-lead data at 2.76 TeV per nucleon-nucleon pairwith an integrated luminosity of just over 9µb-1. The ATLAS inner detector consists of 3 layers ofsilicon pixel detectors and 4 double sided strip layers in the barrel regions, with pixel and strip discscovering the forward region out to |η| = 2.5. Due to the excellent capabilities of the ATLAS detec-tor, and its stable operation during the first heavy ion run, these data allow measurements of thecharged particle spectra and their ratios in different centrality bins over a wide range of transversemomenta and pseudorapidity. Comparison of ATLAS results to the results measured at lower energywill provide the opportunity to study the differences between the medium formed at the LHC andRHIC.

145

Study of Ultraperipheral processes in sqrt(s_NN)=2.76 Pb+Pb col-lisions with the ATLAS detector at the LHCAuthor: Toni Baroncelli1



Besides the study of strongly-coupled matter, heavy ion collisions at the LHC provide opportuni-ties to study photon-nucleus and two-photon reactions in a hitherto unexplored energy regimse.Photoproduction of vector mesons off of the strong electromagnetic fields generated by the highlyLorentz-contracted nuclei provides a tool to study the interactions of quark-antiquark dipoles withstrong gluon fields. This talk presents a first study of these large impact parameter “ultraperipheral”collisions (UPC), with a data set corresponding to up to 9 µb-1 of lead-lead collisions at a nucleon-nucleon center-of-mass energy of 2.76 GeV, recorded by the ATLAS Detector at the LHC. Two-prong

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events are selected with essentially no other activity registered in the rest of the detector, except forforward neutrons measured by the ATLAS zero degree calorimeters. Results on di-muon decays intoJ/psi and other channels will be presented.

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Measurement of higher-order flow harmonics in sqrt(s_NN)=2.76TeV Pb+Pb collisions with the ATLAS detector at the LHCAuthor: Soumya Mohapatra1

1 Department of Physics-State University of New York (SUNY)


Collective harmonic flow and jet-medium interactions are two phenomena under intense study inultra-relativistic heavy ion collisions at RHIC and the LHC. One outstanding question is how to dis-entangle these two contributions for various single and multiple particle observables. Both higher-order harmonic flow (v1, v2, v3, …) and jet-medium interactions, for example, have been argued tobe responsible for several novel structures observed in two-particle∆η and∆ϕ correlations. In thisposter, we present ATLAS measurement of two particle correlation in a broad momentum and cen-trality range. We carry out a Fourier analysis of the correlation function and extract the individualflow harmonics. We compare the first six terms(v1-v6) with those measured independently from anevent plane method. We discuss the impact of these results for disentangling harmonic flow andjet-medium effect, and for understanding the nature of transition from the flow-dominated low pTregion to the jet-dominated high pT region.

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Measurements of Jet Production and Jet Fragmentation in sqrt(s_NN)= 2.76 TeV Pb+Pb Collisions with the ATLAS detector at the LHC

Author: Toni Baroncelli1



The LHC has opened a new kinematic regime for the jet measurements in heavy ion collisions. Withthe factor of 14 increase in collision energy compared to RHIC data, new insights have already beenachieved. The observation of centrality-dependent di-jet asymmetry measured by ATLAS and CMSis strongly suggestive of jet quenching – strong energy loss of parton traversing a hot and denseQCD matter. In this poster we will concentrate on details of single-jet and di-jet measurements inATLAS, in particular on jet energy resolution and background fluctuations. We will also presentresults on jet fragmentation.

Jets / 149

Jet quenching from RHIC to LHCAuthor: Thorsten Renk1

1 University of Jyväskylä

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Despite a wealth of experimental data for high p_T processes in heavy-ion collisions, discriminatingbetween different models of hard parton-medium interactions has been difficult. A large reason isthat the pQCD parton spectrum at RHIC is so steeply falling that distinguishing even a moderateshift in parton energy from complete parton absorption is essentially impossible. In essence, energyloss models are effectively only probed in the vicinity of zero energy loss and as a result, only thepathlength dependence of energy loss offers some discriminating power at RHIC kinematics. AtLHC, this is no longer the case: Due to the much flatter shape of the parton spectra originating from2.76 AGeV collisions, the available data probe much deeper into the model dynamics. A simultane-ous fit of the nuclear suppression both at RHIC and LHC kinematics has thus a huge potential todiscriminate between various models with equally good description of RHIC data alone.

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Effects of parton radiative processes onQuark-GluonPlasma ther-malizationAuthor: Bin Zhang1

Co-author: Warner Wortman 1

1 Arkansas State University


Radiative processes and dynamical screening are important for a precise description of the dynamicsof relativistic heavy ion collisions. When evolutions from inside-outside and thermal initial condi-tions are compared, the parton system produced in relativistic heavy ion collisions is found to beable to overcome expansion and move toward thermalization via parton collisions. Scaling behav-iors show up in both the pressure anisotropy and the energy density evolutions. In particular, thepressure anisotropy evolution shows an approximate coupling constant scaling when radiative pro-cesses are included. It approaches an asymptotic time evolution on a time scale of 1 to 2 fm/c. Theenergy density evolution approaches an asymptotic time evolution that decreases slower than theideal hydro evolution. These observations indicate that partial thermalization can be achieved andviscosity is important for the evolution during the early longitudinal expansion phase of a relativisticheavy ion collision.

Radiative processes are the driving force behind gluon chemical equilibration. The effects of theseprocesses, or of chemical equilibration, on kinetic equilibration can be studied by comparing theevolution with only the elastic process to that including radiative processes. When the initial condi-tion is close to chemical equilibrium, the opening up of the inelastic channels leads to more kineticequilibration. If the initial condition is highly undersaturated, the additional production of particlesquickly leads to smaller cross sections that counteract the increase in the particle number. Thenkinetic equilibration is less sensitive to whether there are radiative processes. On the other hand,kinetic equilibration also affects chemical equilibration. As expected, when there are only elasticprocesses, the system goes farther and farther away from chemical equilibrium. It is interestingto see that systems with the same initial fugacity but different initial pressure anisotropies havedifferent early fugacity evolutions.

In addition to the interplay between chemical equilibration and kinetic equilibration, the pressureanisotropy difference evolution for systems starting from different initial pressure anisotropies isstudied to gain better insight into the approach to the asymptotic evolution. The difference evolutionis found to follow an exponential proper time dependence after a short period of time. In the case thatincludes radiative processes, the larger the coupling constant or the larger the initial energy density,the faster the difference decreases. The evolution curves for different coupling constants and initialenergy densities appear to come from the same point. Pressure anisotropy evolutions from thermalinitial conditions and Color Glass Condensate motivated initial conditions are compared to study theeffects of initial particle momentum distribution. Radiative processes are again shown to make a bigdifference in system evolution. When only the gluon elastic process is included, kinetic equilibration

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is sensitive to the initial momentum distribution. If radiative processes are included, the pressureanisotropy evolution is robust against changes in the initial momentum distribution.

Reference:Parton radiative processes and pressure isotropization in relativistic heavy ion collisions, Bin Zhang,Warner A. Wortman, Phys. Lett. B 693, 24 (2010).


Some new results on high-energy ”jet stopping” in AdS/CFTAuthor: Peter Arnold1

Co-author: Diana Vaman 1

1 University of Virginia


A very basic theoretical question is: How far does a high-energy excitation travel in a quark-gluonplasma, and how does that distance scale with energy? In weak coupling, the stopping distancescales with energy as E^(1/2), up to logarithms. In strongly-coupled plasmas with gravity duals,theorists have found that the maximum stopping distance scales instead like E^(1/3). In the lattercase, we show that there can be an important distinction between typical and maximum stoppingdistances. For the strongly-coupled excitations we study, we find that the typical stopping distancescales as E^(1/4).


Running coupling corrections to high energy inclusive gluon pro-ductionAuthors: William Horowitz1; Yuri Kovchegov2

1 University of Cape Town2 The Ohio State University


We calculate running coupling corrections for the lowest-order gluon production cross section inhigh energy hadronic and nuclear scattering using the BLM scale-setting prescription. In the finalanswer for the cross section the three powers of fixed coupling are replaced by seven factors ofrunning coupling, five in the numerator and two in the denominator, forming a ‘septumvirate’ ofrunning couplings, analogous to the ‘triumvirate’ of running couplings found earlier for the small-xBFKL/BK/JIMWLK evolution equations. We use our lowest-order result to conjecture how runningcoupling corrections may enter the full fixed-coupling kT-factorization formula for gluon produc-tion which includes non-linear small-x evolution. This work is the latest theoretical improvementon the approach used recently by Albacete and Dumitru in arXiv:1011.5161 [hep-ph] to accuratelypredict the centrality dependence of the charged particle multiplicity density measured by ALICEcollaboration.

156

Characterizing quark gluon plasma by Heavy Flavors

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Author: santosh K das1

Co-author: Jan-e Alam 1

1 Variable Energy Cyclotron Centre


The drag and diffusion coefficients of charm and bottom quarks propagatingthrough quark gluon plasma (QGP) have been evaluated for conditionsrelevant to nuclear collisions at Large Hadron Collider (LHC)and at Relativistic Heavy Ion Collision (RHIC).The dead cone and Landau-Pomeronchuk-Migdal (LPM) effects onradiative energy loss of heavy quarks have been considered.Both radiative and collisional processes of energy loss are includedin the \it effective drag and diffusion coefficients.With these effective transport coefficients we solve the Fokker Plank (FP)equation for the heavy quarks executing Brownian motionin the QGP. The solution of the FP equation has been used toevaluate the nuclear suppression factor, RAA and elliptic flow v2 for thenon-photonic single electron spectra resulting from the semi-leptonic decaysof hadrons containing charm and bottom quarks. It is observed thatthe experimental data from RHIC on RAA and v2of nonphotonic electrons can be reproduced simultaneously within thepQCD framework for the same set of input. The RAA and v2 of thenon-photonic electron from heavy mesondecays produced in nuclear collisions at LHC and low energy RHICrun have also been predicted.The effects of mass on RAA

has also been highlighted.

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Heavy quarkonia in a quark-gluon plasma: coupled evolutionand dynamicsAuthor: Nicolas Borghini1

Co-author: Clément Gombeaud 1



We consider the possibility that heavy quarkonia admit different bound states in a QGP, betweenwhich they can transition dynamically. We show that the vacuum mass eigenstates are not therelevant eigenstates for the in-medium dynamics. This leads in particular to abundance ratios of thevarious states which deviate from the predictions of static models. Additionally, the quarkoniumdynamics differ from that of states with a definite mass.

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Study of the expansion and the phase transition of a quarkplasmato an hadron phase with the NJL model using a new QMD ap-proach.Author: Rudy Marty1

Co-author: Joerg Aichelin 1

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1 Subatech


One of the challenges of present day in nuclear physics is the understanding of the phase transitionbetween the quark gluon plasma and the hadronic world. We can divide space into cells to createa lattice of partons, or describe the transformation of energy via the Cooper-Frye formula, but inthese cases we miss some dynamical aspects.

That is why I will present a study of the expansion and the phase transition with a QCD inspiredmodel : the Nambu-Jona-Lasinio (NJL) model. This model is particularly useful to describe quarkmatter at low temperature (below Λ_QCD). It provides an effective mass at finite (T,μ), and thencross sections and decay widths for hadrons (possible mixed phase).

Recent results are presented using these data within a Quantum Molecular Dynamics (QMD) code.This code is designed for local interactions at finite (T,μ). It is a fully relativistic code which isLorentz invariant and avoids the No Interaction Theorem in a different way than previous similarattempts.

Finally we know that there are correlations inside the plasma before the phase transition. We discusshow this scenario can be modeled with these tools to understand this transition in detail and to findobservables which distinguish between the different approaches.

QCD Phase diagram / 159

QCD thermodynamics at intermediate couplingAuthors: Jens Andersen1; Lars Leganger1; Michael Strickland2; Nan Su3

1 Norwegian University of Science and Technology2 Gettysburg College3 Bielefeld University

The weak-coupling expansion of the QCD free energy is known to order g^6*log[g], however, theresulting series is poorly convergent at phenomenologically relevant temperatures. I will discusshow the gauge invariant hard-thermal-loop perturbation theory (HTLpt) reorganization of the cal-culation improves the convergence of the successive approximations to the QCD free energy. I willpresent new results of an HTLpt calculation of QCD thermodynamics to three loops. The results ofthis calculation are consistent with lattice data down to 2-3T_c. This is a non-trivial result since, inthis temperature regime, the QCD coupling constant is neither infinitesimally weak nor infinitelystrong with g~2, or equivalently alpha_s~0.3. Therefore, we have a crucial test of the quasiparticlepicture in the intermediate coupling regime. Our results suggest that HTLpt provides a systematicframework that can be used to calculate static and dynamic quantities for temperatures relevant atLHC.


Moments of chargefluctuations, pseudo-critical temperatures andfreeze-out in heavy ion collisionsAuthor: Frithjof Karsch1

1 Brookhaven National Laboratory


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In the chiral limit and at temperatures close to the QCD phase transition temperature physical ob-servables are expected to show universal properties that are controlled by the symmetry class of a3-dimensional O(4) spin model [1]. Higher moments of net baryon number as well as electric chargefluctuations are sensitive to these universal features of the chiral phase transition [2].

The sixth order moments are the first moments which will diverge in the chiral limit at the QCDphase transition temperature. At non-zero values of the light quark masses the sixth order momentof baryon number fluctuations has a pronounced minimum at a pseudo-critical temperature whichis close to the temperature where fluctuations of the chiral order parameter are the largest.

We present a calculation of the O(4) scaling functions that control scaling properties of the net baryonnumber fluctuations [3]. Using these universal scaling functions as well as PNJL model calculations[4] we show that the sixth order moment of baryon number fluctuations is negative in the vicinity ofthe pseudo-critical temperature for the chiral transition and present new results from lattice calcula-tions using the highly improved staggered fermion action (hisq). These QCD results are in strikingcontrast to hadron resonance gas model calculations. We conjecture that higher order moments ofnet baryon number and electric charge fluctuations are well suited to characterize freeze-out con-ditions in heavy ion collisions. Their experimental analysis in low-energy runs at RHIC as wellas at LHC will allow to verify to what extent freeze-out occurs from a thermal medium close tocriticality.

[1] O. Kaczmarek et al., Phase boundary for the chiral transition in (2+1) -flavor QCD at small valuesof the chemical potential Phys. Rev. D83, 014504 (2011).[2] F. Karsch and K. Redlich, Probing freeze-out conditions in heavy ion collisions with moments ofcharge fluctuations, Phys. Lett. B695, 136 (2011).[3] J. Engels and F. Karsch, The scaling functions of the free energy density and its derivatives forthe 3d O(4) model, in preparation.[4] J. Engels, B. Friman, F. Karsch, K. Redlich and V. Skokov, Fluctuations as probe of the QCD phasetransition and freeze-out in heavy ion collisions at LHC and RHIC, arXiv:1103.3511.

164

Photon and dilepton production from viscous QGPAuthor: Asis Chaudhuri1

Co-author: Bikash Sinha 1



Photons and dileptons are important probe for the lattice QCD predicted deconfined matter, com-monly called Quark-Gluon-Plasma (QGP). Unlike the strongly interacting hadrons, which can giveinformation about the ‘last scattering surface’, electromagnetically interacting photons and dilep-tons give information about the matter at the deep interior. Viscous effects on photon and dileptonproduction is studied recently [1,2]. However, the model [1,2] appears to have some inconsistencythat viscous effects on fluid evolution were not accounted for. In a recent work, we have removedthe inconsistency [3]. Photon production rate from Compton and annihilation processes was convo-luted over the space-time evolution of the QGP, obtained by explicitly solving Israel-Stewart’s 2ndorder theory of hydrodynamics. In viscous dynamics, photon/dilepton production is modified due to(i) changed space-time evolution of the fluid and (ii) non-equilibrium correction to the equilibriumdistribution function. The non-equilibrium correction grows with viscosity as well with transversemomentum. Applicability of viscous hydrodynamics requires that the non-equilibrium correction issmall. Viscous effects on photon and dilepton production are strong [3,4]. Even for AdS/CFT lowerbound of viscosity (η/s=0.08), strong viscous correction render the hydrodynamics inapplicable be-yond pT ~ 1.5 GeV. If QGP viscosity is larger than the Ads/CFT limit, then limitation will be evenmore severe. Photon production as a function of initial time, also suggest that if the inverse slopeparameter of the photon spectra, is measured within an accuracy of ~20-80 MeV, one can possibly

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estimate the initial time and viscosity within reasonable limit. We also find that for dilepton invari-ant mass M~600-900 MeV, the dilepton to photon ratio is sensitive to viscosity to entropy ratio ofthe medium. The dilepton to photon ratio can possibly serve as a ‘viscometer’ for QGP.

[1] K. Dusling, Nucl.Phys.A839(2010)70.[2]K. Dusling and S. Lin, Nucl.Phys A809(2008)246.[3] A. K. Chaudhuri and B. Sinha, Phys. Rev. C83(2011)039405.[4] A. K. Chaudhuri and B. Sinha, to be published.

165

Hydrodynamical analysis of centrality dependence of chargedpar-ticle’s multiplicity in √sNN=2.76 TeV Pb+Pb collisionAuthor: Asis Chaudhuri1

Co-author: Victor Roy 1


Ongoing heavy ion collision at Large Hadron Collider, CERN is expected to settle the importantissues like the possibility of formation of the lattice QCD predicted strongly interacting nuclear mat-ter known as Quark Gluon Plasma (QGP) and the important issue of thermalization and the timetaken by the system to achieve the same. Recently ALICE collaboration [1] measured the centralitydependence of charged particle multiplicity in √sNN=2.76 TeV Pb-Pb collision. The viscous hydrowas pretty successful to describe the experimental particle multiplicity and elliptic flow data at RHICenergy, from which the initial condition of the produced medium can also be traced back. We use2+1D viscous hydrodynamic model to explain the centrality dependence of experimental chargedparticle multiplicity produced in Pb-Pb √sNN=2.76 TeV collision and obtain the initial condition ofthe fluid produced. The space time evolution of the fluid is obtained by solving energy momen-tum conservation along with solving relaxation equation for shear viscous stresses obtained fromIsrael-Stewart’s 2nd order theory. The conservation equation were closed with an equation of state(EOS) constructed from recent lattice data [2] for QGP phase which undergoes a crossover transi-tion to Hadronic phase (comprising all the resonances belowmass 2.5 GeV) at crossover temperatureTco=174 MeV. It was assumed that initial energy density was mostly scaled with number of binarycollision and the system freezes out when the temperature at any space-time points reaches Tf=130MeV. Our study [3] shows that hydrodynamical evolution of QGP fluid, with viscosity to entropydensity ratio η/s=1/4π, initialized to central energy density εi =370 GeV/fm3 at initial time τi=0.6 fm/cor initialized to energy density εi =72 GeV/fm3 at initial time τi=1.0 fm/c explains the ALICE dataon centrality dependence of charged particle multiplicity. Smaller initial time τi=0.2 fm/c do not re-produce the data. Initial time τi=0.6-1.0 fm/c is also consistent with ALICE measurement of chargedparticles pT spectra and elliptic flow. We also show that an alternative of hadronic resonance gas,even at the unphysical high temperature of T=220 MeV do not explains the ALICE data.

[1] K Aamodt et al. [The ALICE collaboration], arXiv : 1011.3916[2] S. Borsanyi et al. JHEP 1011, 077 (2010),[arXiv : 1007.2580[hep-lat]].[3] A.K.Chaudhuri and Victor Roy, arXiv: 1102.4936 [nucl-th].

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Entanglement between deconfinement transition and chiral sym-metry restorationAuthor: Yuji Sakai1

Co-authors: Hiroaki Kouno 2; Masanobu Yahiro 1; Takahiro Sasaki 1

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1 Kyushu University2 Saga University


We extend the Polyakov-loop extended Nambu–-Jona-Lasinio (PNJL) model by introducing an effec-tive four-quark vertex depending on Polyakov loop. The effective vertex generates entanglementinteractions between Polyakov loop and chiral condensate. The new model is consistent with latticeQCD data at imaginary quark numberchemical potential and real and imaginary isospin chemical potentials, particularly on strong corre-lation between the chiral and deconfinement transitions and also on the quark mass dependence ofthe order of the Roberge-Weiss endpoint. We investigate the influence of the entanglement interac-tions on the location of thetricritical point at real isospin chemical potential and on the location of the critical endpoint at realquark number chemical potential.

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Probingnuclear partondensities andparton energy loss processesthrough photon + heavy-quark jet production in p-A and A-A col-lisionsAuthor: Tzvetalina Stavreva1

Co-authors: Francois Arleo 2; Ingo Schienbein 1

1 LPSC2 LAPTH

We present a detailed phenomenological study of the associatedproduction of a prompt photon and a heavy quark jet (charm or bottom) in proton-nucleus (p-A)and nucleus-nucleus (A-A) collisions. The dominant contribution to the cross-section comes fromthegluon–heavy-quark (gQ) initiated subprocess, making this process very sensitive to the gluon andthe heavy-quark nuclear parton densities. We show that the future p-A data to be collected at theLHC should allow one to disentangle the various nPDF sets currently available. In heavy-ion colli-sions, the photon transversemomentum can be used to gauge the initial energy of themassive partonwhich is expected to propagate through the dense QCD medium produced in those collisions. Thetwo-particle final state provides a range of observables (jet asymmetry, photon-jet pair momentum,among others), through the use of which a better understanding of parton energy loss processesin the massive quark sector can be achieved, as shown by the present phenomenological analysiscarried out in Pb-Pb collisions at the LHC.

169

Exotic Matter-Antimatter MoleculesAuthor: Cheuk-Yin Wong1

Co-author: Teck-Ghee Lee 2

1 Oak Ridge National Laboratory2 Auburn University


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In a nuclear collision at RHIC and LHC, a large number of particlesand antiparticles are produced. The production of matter andantimatter particles in close space-time proximity raises theinteresting question whether chance encounters of some of the producedcharged particles and antiparticles may lead to the formation ofexotic matter-antimatter molecules as debris of the collision. Thedetection of new matter-antimatter molecules may be a difficult task.It is nonetheless an interesting theoretical question to investigatethe general factors affecting the stability of matter-antimattermolecules. Using a formalism similar to the previous investigation ofthe X(3872) as a heavy-quark molecular state [1], we find thatmatter-antimatter molecules with charged constituents(m1+,m2-,m2bar+,m1bar-) possess bound states if their constituent massratio m1/m2 is greater than about 4 [2]. This stability conditionsuggests that the binding of matter-antimatter molecules is a rathercommon phenomenon. We evaluate the binding energies of exoticmatter-antimatter molecules (mu+ e-)-(e+ mu-), (pi+ e-)-(e+ pi-),(K+ e-)-(e+ K-), (p e-)-(e+ pbar), (p mu)-(mu+ pbar), and(K+ mu-)-(mu+ K-), which satisfy the stability condition. We estimatethe molecular annihilation lifetimes in their s states.

[1] C. Y. Wong, Phys. Rev. C69, 055202 (2004).[2] C. Y. Wong and T. G. Lee, arXiv:1103.5774 (2011).

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Energy Dependence of the Identified Hadron Elliptic Flow andQCD Phase StructureAuthor: KeJun Wu1

Co-authors: Feng Liu 1; nu xu 2

1 1. Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079, China 2. The Key Laboratory ofQuarkand Lepton Physics (Huazhong Normal University) Ministry of Education, Wuhan, 430079, China

2 1. Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079, China 2. The Key Laboratory ofQuarkand Lepton Physics (Huazhong Normal University) Ministry of Education, Wuhan, 430079, China 3. NuclearScience Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA


One of the most exciting goals for the field of the high-energy nuclear collisions is to understandthe phase structure of matter with partonic degrees of freedom and the transition from partonicphase to hadronic phase. In this talk, we will utilize the elliptic flow (v2) as a tool to address phaseboundary issue. The v2 reflects the early collision dynamics [1]. Using transport models AMPT [2]and UrQMD [3], we study the energy dependence of the identified hadron elliptic flow in Au+Aucollisions. While in high-energy collisions where hadrons are formed dominantly via the processof parton coalescence, we find the observed number of quark scaling in v2 [1] for all hadrons, theviolation of the scaling is evident for collisions at lower energies where the hadronic interactionsbecome dominant. Due to the high baryon density, the violation is particularly strong for the caseof proton and anti-proton. In this talk we will discuss the boundaries of the region of beam en-ergy, above which partonic interactions clearly dominate and below which hadronic interactionsdominate. Other thermodynamic parameters, extracted around the energy region, like freeze-outtemperature and baryonic chemical potential will also be discussed.

References:

[1] J. Adams et al. (STAR Collaboration), Nucl. Phys. A757, 102(2005) andreferences therein.

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[2] Z.W. Lin et al., Phys. Rev. C72, 064901(2005).[3] S. A. Bass et al., Prog. Part. Nucl. Phys. 41, 255(1998).

Heavy flavors / 172

Quarkonium production at the LHC: QCD corrections and newobservablesAuthor: Jean-Philippe Lansberg1

1 IPNO, Université Paris-Sud 11


I will discuss the impact of QCD corrections on the P_T differential cross section for quarkoniumproduction in pp collisions at RHIC, Tevatron and LHC energies, as well as the contributions fromcharm-gluon fusion. I will present comparisons between the predictions of the Color Singlet Modelup to alpha_s^5 with the first LHC data both for J/psi and Upsilon. I will also show predictionsfor the polarisation to be compared with the forthcoming LHC results. Finally, I will motivate theintroduction of new observables meant to better discriminate between the different mechanisms atwork in quarkonium production at the LHC.

Jets / 173

Jets, mach cone, hot spots, ridges, harmonic flow, dihadron andγ-hadron correlations in high-energy heavy-ion collisionsAuthors: Guo-Liang Ma1; Xin-Nian Wang2

1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China2 Nuclear Science Division MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, California 94720


Within the AMPTMonte Carlo model, fluctuations in the initial transverse parton density are shownto lead to harmonic flows. The net back-to-back dihadron azimuthal correlation after subtraction ofcontributions from harmonic flows still has a double peak that is independent of the initial geo-metric triangularity and unique to the jet-induced Mach cone and expanding hot spots distortedby radial flow. The longitudinal structure of hot spots also leads to a near-side ridge in dihadroncorrelation with a large rapidity gap. By successively randomizing the azimuthal angle of the trans-verse momenta and positions of initial partons, one can isolate the effects of jet-induced mediumexcitation and expanding hot spots on the dihadron azimuthal correlation. The double peaks in thenet dihadron and γ-hadron correlation are quantitatively different since the later is caused only byjet-induced Mach cone.

Reference:[1] Guo-Liang Ma and Xin-Nian Wang, arXiv:1011.5249

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Kadanoff-Baym Approach to Thermalization of Gluonic Matter

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Author: Akihiro Nishiyama1

1 University of Tsukuba


In this presentation, we propose the Kadanoff-Baym approach to the early nonequilibrium stage ofultrarelativistic heavy ion collisions and present recent results about equilibration of gluons. Firstwe introduce the Kadanoff-Baym equation and present the proof of H-theorem for given off-shelldynamics of gluons. Next we show entropy production and equilibration with numerical analysesof this equation. Here we have adopted off-shell g ↔ gg effects as scattering processes whichare prohibited in normal quasiparticle approximation. Finally we estimate the equilibration time(~1fm/c) of gluons for the coupling strength g2 = 1.0 and show the significance of off-shell effectsin heavy ion collisions at RHIC and LHC energies.

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Charged-hadronpseudorapidity distributions in theRDMat LHCenergiesAuthor: Georg Wolschin1

1 Heidelberg University


The energy dependence of charged-hadron production in relativistic heavy-ion collisions is investi-gated in a nonequilibrium-statistical relativistic diffusion model (RDM) with three sources [1]. Theo-retical pseudorapidity distributions are compared with PHOBOS AuAu data [2] at RHIC energies ofsqrt(s_NN) = 0.13 and 0.2 TeV including the centrality dependence, and computed for PbPb centralcollisions at LHC energies of 2.76 and 5.52 TeV.

Whereas the quark-gluon fragmentation sources are most important at RHIC energies, the nearlyequilibrated source near midrapidity that arises from gluon-gluon collisions becomes the major ori-gin of particle production at LHC energies. This is confirmed in a comparison with recent ALICEdata on charged-hadron pseudorapidity distributionsin 2.76 TeV PbPb [3]. The midrapidity dip is determined by the interplay of the three sources[4].

[1] G. Wolschin, Prog. Part. Nucl. Phys. 59 (2007) 37.

[2] B. Alver et al. (PHOBOS Collaboration), Phys.Rev.C 83 (2011) 02491.

[3] K. Aamodt et al. (ALICE Collaboration), Phys. Rev. Lett. 105 (2010) 25230;Phys. Rev. Lett. 106 (2011) 032301.

[4] G. Wolschin, arXiv:1102.3388 (2011); Phys. Lett. B, in press.

Jets / 176

Suppression of high p_T hadrons in PbPb Collisions at LHCAuthor: Xin-Nian Wang1

Co-authors: Enke Wang 2; Hanzhong Zhang 2; Tetsufumi Hirano 3; Xiao-fang Chen 2

1 IOPP / LBNL2 IOPP

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3 Tokyo University


Nuclear modification factor RAA(pT ) for large transverse momentum pion spectra in Pb + Pbcollisions at

√s = 2.76 TeV is predicted within the NLO perturbative QCD parton model. Effect of

jet quenching is incorporated through medium modified fragmentation functions within the higher-twist approach. The jet transport parameter that controls medium modification is proportional tothe initial parton density and the coefficient is fixed by the RHIC data on suppression of large pThadron spectra. Data on charged hadron multiplicity dNch/dη = 1584 ± 80 in central Pb + Pbcollisions from the ALICE Experiment at the LHC are used to constrain the initial parton densityboth for determining the jet transport parameter and the 3+1D ideal hydrodynamic evolution of thebulk matter that is employed for the calculation of RPbPb(pT ) for neutral pions

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A few new experimental results on particle correlationsAuthor: Stefania Velica1

1 Faculty of Physics, University of Bucharest


The study of the correlations among the particles emitted from the overlapping region of the col-liding nuclei gives the information about the conditions in the early stage of the collision and thesystem evolution. The analysis of correlations and fluctuations in the relativistic nuclear collisionsaddresses fundamental aspects of the quantum chromodynamics (QCD) and, therefore, to the prop-erties of strongly-interacting matter at extreme density and temperature.In this work we present the study of correlations between physical quantities describing the be-haviour of different charged particle types providing information on the formation of a new phaseof the highly excited and dense nuclear matter. In this analysis were used the experimental resultsobtained in Au-Au and proton-proton collisions at with the BRAHMS experiment at RHIC. Using theusual methods from statistics and probability theory, we introduce a linear correlation coefficient forthe longitudinal and transverse momentum components and for rapidity and transverse momentumfor all charged particles ( , , and ) produced and detected with the BRAHMS experiment. For provingthe existence of anomalous states in nuclear matter, unusual correlations between the longitudinaland transverse momenta should be observed in the rapidity range -0.1 < y < 3.5. It is, also, proposedthat the change in pT spectra at high rapidities could be one of the possible signals of QGP forma-tion. These results are compared with others obtained in a large energy range, from the JINR DubnaSynchrophasotron, up to CERN SPS, for symmetric and asymmetric collisions. Interesting anomalstates of the nuclear matter can be observed.

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V1 flow componet at LHCAuthor: Laszlo Pal Csernai1

Co-authors: D.D. Strottman 2; H. Stoecker 3; V.K. Magas 4

1 University of Bergen2 Frankfurt Institute for Advanced Studies3 Univ. of Frankfurt4 Univ. of Barcelona

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Substantial collective flow is observed in collisions between Lead nuclei at LHC as evidenced by theazimuthal correlations in the transverse momentum distributions of the produced particles.

We perform simulations [1] of the Pb+Pb heavy ion collisions at LHC at 1.38 + 1.38 TeV/nucl withinthe three module model. The initial stages of the reaction, before the thermal equilibrium is reached,are simulated in terms of effective string rope model [2], based on longitudinally expanding stringsof the color-magnetic field. The produced initial state is tilted, and, thus, the direction of the largestpressure gradient is pointing in the “anti-flow” direction, what resulted in anti-flow peaks in simu-lations for RHIC and SPS [3]. However, one should not forget that this initial state also has a flowvelocity distribution, which tends to further rotate it, and, thus, the direction of the strongest pres-sure gradient will change with time. The intermediate stages of the reaction are simulated with a(3+1)-dimensional fluid dynamical model, using the Particle in Cell (PIC) method adapted to ultra-relativistic heavy ion collisions. The matter expands until it reaches freeze-out, which is treated inthe third module of our model.

The resulting elliptic flow, v2, is in reasonable agreement with the data [4]. Furthermore, our cal-culations also indicate that the v1-flow, which was rather weak at RHIC and SPS, and peaked atnegative rapidities (named as 3rd flow component or anti-flow), now at LHC is expected to peakat forward rapidities (at the same side and direction as the projectile residue), and it may becomestronger [1].

Thus, v1-flow provides a sensitive barometer to estimate the pressure and transport properties ofthe Quark-Gluon Plasma. In order to better study the transverse momentum flow dependence wesuggest a new “symmetrized v1s” flow component, and make predictions for it.

[1] L.P. Csernai, V.K. Magas, H. Stocker, D.D. Strottman, arXiv:1101.3451 [nucl-th].[2] V.K. Magas, L.P. Csernai, and D.D. Strottman, Phys. Rev. C 64 (2001) 014901; Nucl. Phys. A 712(2002) 167.[3] L.P. Csernai, D. Rohrich, Phys. Lett. B 458 (1999) 454; B. Bauchle et al., J. Phys. G 34 (2007) s1077.[4] K. Aamodt et al. [The ALICE Collaboration], Phys. Rev. Lett. 105 (2010) 252302.

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Canwe see from jet quenching that quark-gluon plasma becomesmore perturbative at LHC than at RHICAuthor: Bronislav Zakharov1

1 Landau Institute


We study the nuclear modification factor R_AA at RHIC and LHC energies. We account for theradiative and collisional energy losses. Both the contributions are calculated with running \alpha_saccounting for fluctuations of the jet path lengths. The effect of the thermal suppression of \alpha_sis investigated. Comparison of the theoretical results with the experimental data obtained at RHICand in the ALICE experiment at LHC demonstrates that the experimental R_AA may be describedin pQCD with the entropy extracted from the multiplicity data. However for LHC the thermal sup-pression of \alpha_s should be stronger. This fact demonstrates that at LHC the quark-gluon plasmabecomes more perturbative.

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Dilepton interferometry: a tool to characterize different phasesof matter produced in heavyion collisions

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Author: payal mohnaty1

Co-authors: Bedangadas Mohanty 2; Jane Alam 1

1 Variable Energy Cyclotron Centre2 Variable Energy Cyclotron centre


The Hanbury-Brown-Twiss (HBT) radii from the correlation functions ofthe two virtual photons produced in the collisions of two nuclei atultra-relativistic energies have been evaluated. We show that a study of the mass dependence ofvarious interferometry radii extracted from the correlation functions of virtual photons can be apowerful toolto characterize and distinguish the hadronic and the partonic phases.It is shown that the non-monotonic variation of the HBT radii with invariant mass provides an accessto the development of collective flow in the system.The sensitivity of the results on the initial thermalization timeis also examined.

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Charged Particle’s elliptic flow in 2+1D viscous hydrodynamicsat LHC (√s=2.76 TeV) Energy in Pb+Pb collision. and QGP viscos-ity

Author: Asis Chaudhuri1

Co-author: Victor Roy 1


The azimuthal correlation of produced particles in the reaction plane or elliptic flow in heavy ioncollision is a sensitive probe to (i) degree of thermalization (ii) transport coefficient and (iii) the equa-tion of state (EoS) of the medium. Recently, ALICE collaboration measured (differential) elliptic flowin √s=2.76 TeV Pb-Pb collision [1]. We have analyzed the elliptic flow data to obtain an estimate ofviscosity to entropy ratio η/s at LHC energy. Details can be found in [2]. In Israel-Stewart’s secondorder theory of hydrodynamics, we have simulated elliptic flow in 2.76 TeV Pb+Pb collisions. Wehave assumed that initial Pb+Pb collisions produces aQGP fluid which thermalizes in the time scale, τi=0.6 fm/c. Hydrodynamical evolution of the fluid isgoverned by a lattice motivated equation of state with confinement-deconfinement cross-over tran-sition at Tc=174 MeV. The initial condition of the fluid was fixed to reproduce ALICE measurementsfor charged particles multiplicity in 0-5% collisions. Ideal QGP fluid require rather large initial en-ergy density, ei=90 GeV/fm^3. Initial energy density is reduced if the fluid is viscous, e.g. ei =78,70, 60 GeV/fm^3 for viscosity to entropy ratio η/s=0.08, 0.12 and 0.16 respectively. ALICE data forcharged particles elliptic flow in 20-30%, 30-40% and 40-50% collision are best explained for fluid vis-cosity η/s=0.08. In very central 10-20% collisions however, ALICE data prefer ideal fluid rather thana viscous fluid. We conclude that nearly perfect fluid is consistent with the ALICE data for ellipticflow in 2.76 TeV Pb+Pb collisions.

[1] K.Aamodt et al. arXiv: 1011.3914[nucl-ex].[2] Victor Roy and A.K. Chaudhuri , [arXiv: 1103.2870[nucl-th]].

Electromagnetic probes / 184

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Enhancement of thermal photon production in event-by-eventhydrodynamicsAuthor: Rupa Chatterjee1

Co-authors: Hannu Holopainen 1; Kari Eskola 1; Thorsten Renk 1

1 University of Jyvaskyla


Thermal photon emission is widely believed to reflect properties of the earliest, hottest evolutionstage of the medium created in ultra-relativistic heavy-ion collisions. Previous computations ofphoton emission have been carried out using a hydrodynamical medium description with smooth,averaged initial conditions. Recently, more sophisticated hydrodynamical models which calculateobservables by averaging over many evolutions with event-by-event fluctuating initial conditions(IC) have been developed. Given their direct connection to the early time dynamics, thermal photonemission appears an ideal observable to probe fluctuations in the medium initial state. In this work,we demonstrate that including fluctuations in the IC may lead to an enhancement of the thermalphoton yield of about a factor of 2 in the region 2 < pT < 4GeV/c (where thermal photon productiondominates the direct photon yield) compared to a scenario using smooth, averaged IC. Consequently,a better agreement with PHENIX data is found. This can be understood in terms of the strongtemperature dependence of thermal photon production, translating into a sensitivity to the presenceof ‘hotspots’ in an event and thus establishing thermal photons as a suitable probe to characterizeIC fluctuations.Ref:arXiv:1102.4706[Hep-ph].


Initial conditions - Theory perspectives

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Initial state fluctuations and their effect on the flowAuthor: Volodymyr Magas1

Co-authors: Daniel Strottman 2; Horst Stoecker 3; Laszlo Csernai 4

1 University of Barcelona2 LANL3 University of Frankfurt4 University of Bergen


Substantial collective flow is observed in collisions between Lead nuclei at LHC as evidenced by theazimuthal correlations in the transversemomentumdistributions of the produced particles [1].

We perform simulations of the Pb+Pb heavy ion collisions at LHC at 1.38 + 1.38 TeV/nucl withinthe three module model. Our calculations, in particular, show that the v1-flow, which was ratherweak at RHIC and SPS, becomes stronger at LHC. Another even more important change in thev1 behaviour with respect to the similar simulations for RHIC [2] is that the v1 now peaks in the“forward” direction [3], i.e. positive v1 peak appears now at positive rapidity, and correspondinglynegative peak at negative rapidity, contrary to what was observed at RHIC.

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However, it also appears that v1 flow is extremely sensitive to the initial state fluctuations, due tothe sharp change around y=0.One has to take into account that the Center of Mass (CM) rapidity is not exactly the same for allcollisions, due to random fluctuations in the initial state, where the numbers of participant nucleonsfrom projectile and target may not be exactly the same. This leads to considerable y_CM fluctua-tions at large impact parameters, where the flow asymmetry is the strongest, while total number ofparticipants is the smallest.

To analyze the consequences of these fluctuations, we assumed a Gaussiany_CM distribution, centered at y_CM=0, with variance of 1 or 2 units of rapidity. Such fluctuationsstrongly reduce v1(y) at central rapidities, however, it still stays large enough to be observed and todemonstrate the “rotation effect” discussed above [3].

It is also important to take into account experimental rapidity cuts of ALICE detector. These cutstogether with initial state CM rapidity fluctuations result also into some increase of the elliptic flow,v2(pt), putting it in better agreement with the ALICE data.

1) K. Aamodt et al. [The ALICE Collaboration], arXiv:1011.3914 [nucl-ex].2) B. Bauchle et al., J. Phys. G 34 (2007) s1077.3) L.P. Csernai, V.K. Magas, H. Stocker, D.D. Strottman, arXiv:1101.3451 [nucl-th].

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Pionquenching and tomography fromRHIC to LHC in theWHDGmodelAuthor: Miklos Gyulassy1

Co-author: William Horowitz 2

1 Columbia University2 University Cape Town


We present parameter-free predictions from the WHDG (radiative+elastic+geometric fluctuation)energy loss model for high pT pion suppression in A+A at 2.76 and 5.5 ATeV. The input density isconstrained from a rigorous statistical analysis of RHIC pi0 quenching data. The predictions areconsistent with the recent charged hadron RAA data from ALICE only within the current very largesystematic uncertainty (due to the unmeasured reference p + p spectrum). However, our constrainedprediction of central to peripheral pion R_cp(pT), in which reference p + p spectra uncertaintiescancel, is found to be over-quenched by ~two sigma relative to the charged hadron ALICE R_cp dataat all pT<20 GeV.The basic tomographic assumptions inWHDG are (1) the energy loss scales linearlywith the initial QGP density, rho0, and (2) that rho0 scales linearly with charge particle multiplicitydNch/dy. Under these assumptions, WHDG predicts significant difference in magnitude and pt slopepf pion RAA between RHIC and LHC. Future ALICE identified pi,K,p hadron RAA data (as well asaccurate p + p and p + Pb reference data) will enable more quantitative jet tomographic tests of hardprobe dynamics in strongly interacting quark gluon plasmas.

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High resolution numerical scheme for hydrodynamic analysis ofheavy ion collisions and formation of an incoming shock waveinduced by reheatingAuthor: Masayuki Asakawa1

Co-authors: Hideaki Takabe 1; Keita Takakura 1; Luca Baiotti 1; Masakiyo Kitazawa 1; Masatsugu Isse 2

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1 Osaka University2 Kobe City College of Technology


We analyze hydrodynamic evolution of fireballs created byrelativistic heavy ion collisions by applying a high resolutionscheme of numerical hydrodynamics with a focus on the possibilityof shock formation in the course of time evolution.

The possibility of shock formation has not been taken intoaccount seriously in numerical analysis of relativistic heavy ion collisions. State of art high resolu-tion codes which are capable of capturing shocks have not been adopted with few exceptions.The possibility of shock formation or discontinuity is an importantfeature of hydrodynamics, and this should be treated carefully.We have developed a computational code on the basis of Chakravarthy-Osher scheme, which is oneof flux-vector splitting schemes and is known to reproduce shock waves well in numerical simu-lations for a variety of situations. When equation of states with a first order phase transition isemployed, our simulation reveals the manifestations of shock wavesand shock-like structures hav-ing a sharp edge, which are blurred by numerical viscosity in previous analyses, during the timeevolution of fireballs. In particular, we find a high temperature region surrounded by sharp edgesowing to the reheating of matter at early stage, and the formation of incoming shock-wave inducedby this high temperature region. We will clarify the mechanism that produces these novel structuresand discuss their importance for the observables in heavy ion collisions.

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Bulk viscosity of a pion gas and energy-momentum correlations

Author: Juan Torres-Rincon1

Co-authors: Antonio Dobado 1; Felipe Llanes-Estrada 1

1 Universidad Complutense de Madrid


We address the bulk viscosity of a pion gas in kinetic theory.Using Unitarized Chiral PerturbationTheory for the pion interaction we show how elastic collisionscontrol the bulk viscosity at lowtemperature and physical pion masses. The bulk viscosity vanishes in the limit of zero temperature,in agreement with non-relativistic arguments. The collision integral zero modes (correspondingto particle and energy conservation) are properly taken into account, as is the approximate pionchemical potential.We also propose a way of measuring the bulk viscosity incorrelations of the fluctuating part of the stress-energy tensor andshow how an estimate can be obtained with data in heavy ion collisionsat LHC or FAIR.


ATLAS flowCorresponding Author: [email protected]

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Collectiveflowmeasurements from thePHENIXExperimentCo-author: Shinichi Esumi 1

1 Institute of Physics - University of Tsukuba


Recent collective flow measurements including higher momentevent anisotropy from the PHENIX experiment will be presented,the particle type, beam energy dependence and the relation withjet modification will be discussed.


Common discussion with 4 experimental speakersCorresponding Author: [email protected]


Nuclear modification factors from the CMS experimentCorresponding Author: [email protected]

We report the measurement of transverse momentum spectra of the charged hadrons and photonsin √sNN = 2.76 TeV PbPb collisions with the CMS detector. The nuclear modification factors areconstructed by dividing the PbPb pT spectra,normalized to the number of binary collisions, by the pp references.


Recent R_AA Results from the PHENIX ExperimentCorresponding Author: [email protected]


Common discussion with 4 speakersCorresponding Author: [email protected]


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Jet measurements by the CMS experiment in pp and PbPb colli-sions


The energy loss of fast partons traversing the strongly interacting matterproduced in high-energy nuclear collisions is one of the most interestingobservables to probe the nature of the produced medium. The multipurposeCompact Muon Solenoid (CMS) detector is well designed to measure these hardscattering processes with its high resolution calorimeters and high precisionsilicon tracker. Analyzing data from pp and PbPb collisions at a center-of-massenergy of 2.76 TeV parton energy loss is observed as a significant imbalance ofdijet transverse momentum. To gain further understanding of the parton energyloss mechanism the redistribution of the quenched jet energy was studied usingthe transverse momentum balance of charged tracks projected onto the directionof the leading jet. In contrast to pp collisions, a large fraction the momentumbalance for asymmetric jets is found to be carried by low momentum particles atlarge angular distance to the jet axis. Further the fragmentation functions forleading and subleading jets were reconstructed and are compared to modelcalculations and measurements in pp collisions. The results confirm andcomplement earlier CMS results based on calorimeter jets and yield a detailedpicture of parton propagation in the hot QCD medium.


ATLAS jet measurements






Heavy-flavor production in PbPb collisions at the LHCmeasuredwith the ALICE detector


The ALICE experiment studies nucleus–nucleus collisions at the LHC in order to investigate theproperties of QCD matter at extreme energy densities. The measurement of open charm and openbeauty production allows to investigate the mechanisms of heavy-quark propagation, energy lossand hadronization in the hot and dense medium formed in high-energy nucleus-nucleus collisions.In particular, in-medium energy loss is predicted to be different for massless partons (light quarksand gluons) and heavy quarks at moderate momentum.The ALICE apparatus allows us to measure open heavy-flavour particles in several decay channelsand with a wide phase-space coverage.

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We present the first results on the nuclear modification factors for heavy flavour particle productionin Pb–Pb collisions at psNN = 2.76 TeV.Using proton–proton and lead–lead collision samples at ps = 7 TeV and psNN = 2.76 TeV, respectively,recorded during 2010, nuclear modification factors RAA(pt) were measured for D mesons at centralrapidity (via displaced decay vertex reconstruction), and for electrons andmuons from heavy flavourdecays, at central and forward rapidity, respectively.





Quarkonium measurements at the LHC with the ALICE detec-tor


ALICE detector has excellent performances to study quarkonium production inheavy-ion collisions at the LHC collider [1]. In this new energy regime, charmonium could reveal aprivileged probe to study the properties of the high-density strongly interacting system formed inthe early stages of high-energy heavy-ion collisions [2].Bottomonium resonances will be abundantly produced, providing new constrains on theoreticalmodels of quarkonium dissociation in QCD matter [1]. Additionally, ALICE will study quarkoniumproduction in proton-proton collisions in which high particle multiplicity events could lead to theformation of high energy density matter as in heavy ions collisions [3].In ALICE [4], quarkonium is measured down to pT = 0 via their mu+mu− decay channels in theALICE muon spectrometer and via their e+e- in the ALICE central barrel. After a short descriptionof the apparatus, the transverse momentum and rapidity distributions of inclusive J/Psi productioncross section in proton-proton collisions at LHC energies will be presented. We will discuss thedependence on charged particle multiplicity of J/Psi yield in proton-proton collisions at sqrt(s) = 7TeV.The number of reconstructed tracklets (η<1.6) in the silicon pixel detector is exploited to measurethe charged particle density at mid- rapidity. Finally, the analysis of the inclusive J/Psi productionin Pb-Pb collisions at a centre of mass energy of sqrt(sNN) = 2.76 TeV will be described. Preliminaryresults on the nuclear modification factor (RAA) and the central to peripheral nuclear modificationfactor (RCP) will be shown.

[1] ALICE collaboration, PPR II, J. Phys. G32, 1295 (2006)[2] P. Braun-Munzinger and J. Stachel, Phys. Lett. B490, 196 (2000); R.L. Thews, M. Schroedter andJ. Rafelski, Phys. Rev. C63, 054905 (2001); A. Andronic et al., Phys. Lett. B571, 36 (2003); L.Grandchamp, R. Rapp and G.E. Brown, Phys. Rev. Lett., 92, 212301 (2004).[3] K. Werner et al. arXiv:1010.0400v1 (2011); K. Werner et al., Phys. Rev. Lett. 106, 122004 (2011).[4] ALICE collaboration, J. Instrum. 3, S08002 (2008).



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203

Hadrochemistry – theory status

204

ALICE hadrochemistry

205

common discussion with 2 speakers


STAR: results from the beam energy scan program



NA49/NA61: SPS results on fluctuations & correlations



Production of identified particles in pp and PbPb collisions atLHC energies with the ALICE detector


The ALICE experiment is taking data since 2009, with proton and lead beams. In this talk, we reviewthe different particle identification techniques used by the experiment and the excellent performanceduring the first year of data taking. We summarize the current results on identified particle spectrain pp collisions at sqrt(s) = 900 GeV and 7 TeV, and in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. Inparticular, the energy dependence of the spectral shapes of the pp data is discussed and the resultsare compared to previous experiments and commonly used Monte Carlo models. The evolutionof the particle spectra in PbPb with collision centrality is presented. Various particle ratios are

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shown, including the baryon/meson ratio (Lambda/K0s). Finally, we conclude with an overview ofthe ongoing analyzes on identified particles.


Correlations and fluctuations measured by the CMS experimentin pp and PbPb collisions


Measurements of charged dihadron angular correlations are presented inproton-proton (pp) and Lean-Lead (PbPb) collisions, over a broad range ofpseudorapidity and azimuthal angle, using the CMS detector at the LHC. In veryhigh multiplicity pp events at center-of-mass energy of 7 TeV, a striking“ridge”-like structure emerges in the two-dimensional correlation function forparticle pairs with intermediate pT of 1-3 GeV/c, in the kinematic region 2.0 <|Delta eta| < 4.8 and small Delta Phi, which is similar to the observation inheavy-ion collisions. Updated studies of this new effect as a function ofparticle transverse momentum, rapidity and event characteristics are shown anddiscussed in comparison to various model calculations. The long-range andshort-range dihadron correlations are also studied in PbPb collision at anucleon-nucleon center-of-mass energy of 2.76 TeV. The dependence of the jet-and ridge-regionshape and yield on transverse momentum and collisioncentrality has been measured. A Fourier analysis of the long-range dihadroncorrelations will be presented and discussed in the context of CMS measurements of higher orderflow coefficients.

New challenges / 210

The low energy frontier of A-A



Physics opportunities of future p-A runs



Physics opportunities of e-A colliders


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Physics opportunities of e-A colliders

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The high energy frontier of A-A

Future facilities and experiment upgrades / 215

eA collisions at the Large Hadron-electron ColliderAuthor: Nestor Armesto Perez1

1 Universidade de Santiago de Compostela


I will show the possibilities for electron-ion studies offered by the proposed electron-hadron col-lider at CERN, the Large Hadron-electron Collider [1]. After a short introduction on open problemsat small x, I will briefly present the machine and detector. Then I will focus on small-x aspects inelectron-nucleus collisions, first on inclusive measurements and the determination of nuclear par-ton densities, and then on diffraction. I will finish by discussing some opportunities for final statestudies.

[1] M. Klein et al., Prospects for a Large Hadron Electron Collider (LHeC) at the LHC, EPAC’08,11th European Parti cle Accelerator Conference, 23- 27 June 2008, Genoa, Italy; http://cern.ch/lhec.

216

Hadrochemistry – theory status

217

ALICE hadrochemistry

218

common discussion with 2 speakers

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Quark production far from equilibriumAuthors: Daniil Gelfand1; Jens Pruschke1; Jürgen Berges1

1 TU Darmstadt

We show that quantum effects dramatically enhance the production of quarks during nonequilib-rium bosonic instabilities. Standard semi-classical descriptions based on the Dirac equation with ahomogeneous background field fail to describe nonequilibrium fermion production in presence ofnon-perturbatively high boson occupation numbers. Our analysis goes beyond this approximationby taking into account quantum corrections including scattering and decay processes, as well asoff-shell and memory effects. This is done in a quark-meson model by using two-particle irreducible(2PI)effective action techniques, which we compare to results from real-time lattice simulations. As aconsequence fermions rapidly approach a quasi-stationary distribution with a thermal occupancy inthe infrared, while bosons enter a turbulent scaling regime. We also illustrate the transition betweena quasi-particle like excitation spectrum towards a strongly correlated medium.

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The Very High Momentum Particle Identification Detector at AL-ICEAuthor: Gergo Hamar1

1 MTA KFKI RMKI Research Institue for Particle and Nuclear Physics


Based on the results in the RHIC heavy ion experimentsthe identification of very high pT particlesseems to be extremely interesting at LHC energies.ALICE performes an excellent event by event PID below 5 GeV/ceven in those high track densities. However, the track-by-trackanalysis of the heavy ion data demands further efforts onthe experimental side.

We are presenting the idea of an ALICE upgrade detector whichis capable to extend the particle identification into themomentum region of 5-25 GeV/c on track-by-track basis.The Very High Momentum Particle Identification Detector (VHMPID)is a gaseous Cherenkov detector, capable to distinguishcharged pions, kaons and protons/antiprotons in the abovemomentum window in event by event. This feature gives us thepossibility to study the meson/baryon anomaly,multi jet fragmantation function, in medium effectsand the same-side and away-side jet correlations.

The talk is focused on design issues and technicalaspects of such a detector, with present simulationand the prototype test results of the VHMPID.

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Highly-anisotropic and strongly-dissipative hydrodynamics forearly stages of relativistic heavy-ion collisions.

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Author: Radoslaw Ryblewski1

1 Institute of Nuclear Physics PAN


A new framework of highly-anisotropic hydrodynamics is introduced [1] that includes dissipationeffects. Dissipation is defined by the form of the entropy source that depends on the pressureanisotropy and vanishes for the isotropic fluid. With a simple ansatz for the entropy source obey-ing general physical requirements, we are led to a non-linear equation describing the time evolu-tion of the anisotropy in purely-longitudinal boost-invariant systems. Matter that is initially highlyanisotropic approaches naturally the regime of the perfect fluid. Thus, the resulting evolution agreeswith the expectations about the behavior of matter produced at the early stages of relativistic heavy-ion collisions.

The equilibration is identified with the processes of entropy production. For purely longitudinal,boost-invariant expansion with small anisotropy, the proposed model agrees with the Israel-Stewarttheory and Martinez-strickland model [2,3,4]. However, the model is designedto describe highly anisotropic systems where the standard dissipative hydrodynamics is not applica-ble.

The proposed model of isotropization may be also used to describe non-boost-invariant systems [5]and boost-invariant systems with asymmetric transverse expansion [6]. In the latter case, we findthat as long as the initial energy density profile is unchanged the calculated soft hadronic observablesremain practically the same. This result indicates the insensitivity of the analyzed observables tothe initial pressure anisotropy and suggests that the complete thermalization of the system may bedelayed to easily acceptable times of about 1 fm/c.

1. W.Florkowski, R.Ryblewski, Phys.Rev. C83 (2011) 034907

2. M.Martinez, M.Strickland, Nucl.Phys. A848 (2010) 183-197

3. M.Martinez, M.Strickland, arXiv:1011.3056 [nucl-th]

4. R.Ryblewski, W.Florkowski, Acta Phys.Polon. B42 (2011) 115-138

5. R.Ryblewski, W.Florkowski, J.Phys.G G38 (2011) 015104

6. R.Ryblewski, W.Florkowski, arXiv:1103.1260 [nucl-th]

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Fireball fragmentation and rapidity correlations of protonsAuthor: Martin Schulc1

Co-author: Boris Tomasik 1

1 Faculty of Nuclear Sciences and Physical Engineering (FNSPE)-Cze


We investigate proton rapidity correlations for a fireball that fragments due to non-equilibrium ef-fects at the phase transition from deconfined to hadronic phase. Such effects include spinodal frag-mentation in case of first order phase transition at lower collision energies and cavitation due tosudden rise of thebulk viscosity at the crossover probed at LHC and the RHIC. The study is performed on samples ofartificial events generated by means of Monte Carlo generator DRAGON. Correlation function inrelative rapidityappears to be a sensitive probe of fragmentation. Resonance decays make the strength of the corre-lation even stronger.Correlation function is compared with experimental results from experiments at collision energies

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of few GeV per nucleon.We demonstrate that there is no principal disagreement between the generated and the experimentalcorrelation functions.


Deconfinement and chiral transition in QCD at finite tempera-tureAuthor: Peter Petreczky1

1 BNL


I will discuss new lattice results on the deconfinement andchiral aspects of the transition in QCD at nonzero temperature.I will report on calculations performed using the Highly ImprovedStaggered Quark (HISQ) action on Nt=6, 8 and 12 lattices. I willshow the continuum extrapolation for several quantities that are discussed in connection with thetransition at nonzero temperatureas well as the determination of the chiral transition temperature in the continuum limit. I will alsoshow new calculations with theasqtad action on Nt=12 lattices which, when combined with the previous Nt=8 HotQCD calculations,give a consistent result for the transition temperature in the continuum limit. Finally I will discussnew findings for the equation of state for HISQ and asqtad actions.

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Jet properties in \it p+p and their possible modification in coldnuclear matter in STARAuthor: Mriganka Mouli MONDAL1

1 Institute of Physics, Bhubaneswar

The intrinsic transverse momentum of partons and the possible initial and final state gluon radiationassociated with hard scatterings give rise to an acoplanarity of di-jets which depends on both theQ2 of hard scatterings and the center of mass energy of the colliding beams. Multiple scatteringsof the hard scattered partons in cold nuclear matter may also alter the measured acoplanarity whencompared to those in \it p+p. Studies in central \it d+Au collisions are therefore vital to disentanglemedium-induced kt broadening from initial state nuclear effects and any potential broadening dueto jet quenching in the medium produced in heavy-ion collisions. While full jet reconstruction is adirect way to study such acoplanarities, di-hadron correlations with respect to a high momentumleading particle can also be utilized as a complementary tool.

Two quantities commonly used to characterize the properties of jets are jt, the transversemomentumof the jet fragments relative to the jet axis, and kt, the transverse component of the momentum ofthe hard scattered partons. Measurements of the jet parameters,

√⟨j2t ⟩ and

√⟨k2t ⟩ at STAR in \it

p+p collisions at√s = 62.4, 200 and 500 GeV extracted from di-hadron correlations are presented.

π0 (Et = 6.5 to 18.5 GeV) and charged tracks (pt = 3.0-8.5 GeV/c) are used as trigger particles inthese analyses. The results extracted at

√s = 200 GeV will be compared to those using full jet

reconstruction and contrasted to measurements made for several \it d+Au centralities.

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Cavitation and Thermal Dilepton Production in QGPAuthor: Sreekanth V.1

Co-authors: Hiranmaya Mishra 1; Jitesh Bhatt 1

1 Physical Research Laboratory, Ahmedabad, India

We investigate the thermal dilepton production-rates using one dimensional boost-invariant secondorder relativistic hydrodynamics to find proper time evolution of the energy density and the temper-ature. We study the \textitnon-ideal effects arising due to viscosity (both bulk and shear), equationof state (ϵ = 3P ) and cavitation on thermal dilepton production from QGP at RHIC energies. Theeffect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consis-tent with recent lattice QCD estimates. It is shown that the \textitnon-ideal gas equation of statei.e ϵ − 3P = 0 behavior of the expanding plasma, which is important near the phase-transitionpoint, can significantly slow down the hydrodynamic expansion and thereby increase the dileptonproduction-rates. We calculate the first order corrections to the dilepton production rates due toshear and bulk viscosities. It is shown that ignoring the cavitation can lead to a wrong estimationof the particle spectra. We show that the shear viscosity can enhance the thermal dilepton spec-tra whereas the bulk viscosity can suppress it. We present the combined effect of bulk and shearviscosities on the dilepton spectra.

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D+→K- π+ π+ Production in pp collisions at LHCwith the ALICEdetectorAuthor: Bala Renu1

1 INFN,Turin


ALICE is the dedicated heavy-ion experiment at the LHC. Its main physics goal is to study the prop-erties of the strongly-interacting matter in the conditions of high energy density (>10 GeV/fm3 ) andhigh temperature (> 0.3 GeV) expected to be reached in central Pb-Pb collisions. Charm and beautyquarks are a powerful tool to investigate this high density and strongly interacting state of matteras they are produced in initial hard scatterings, and due to their long life time, they probe all thestages of the system evolution. The measurement of charm production cross section in pp collisionsprovides interesting insight into QCD processes and is important as a reference for heavy ion stud-ies. Here, we will present the strategy adopted to measure the cross section of one of the hadronicdecay channel, D+→ K- π+ π+ , in pp collisions at LHC energies. The first preliminary cross sectionresults obtained for the same channel will also be shown.

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First results from hybrid HKM for top RHIC and LHC energies

Author: Iurii Karpenko1

Co-authors: Klaus Werner 2; Yuriy Sinyukov 1

1 Bogolyubov Institute for Theoretical Physics2 SUBATECH, University of Nantes

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The hydrokinetic approach [1,2] to A+A collisions describes hydrodynamic expansion of systemscreated in A+A collisions and their dynamic decoupling according to particle liberation probabilitiesin a way inspired by Boltzmann equation. The up-to-date version of hydro-kinetic model includethe realistic features of heavy ion collisions typical for RHIC and LHC energies in the way directedby the papers [3,4]:

• The equation of state (EoS) is constructed for the case of crossover QGP-HG phase transition andcombines lattice-QCD inspired results for QGP phase and ideal gas mixture of all hadron species,well-established by Particle Data Group (326 sorts).

• Gradual decay of short-lived resonances into expanding hadronic system according to theirwidthsdefine the composition of the gas and hence its EoS at each space-time points. The decays con-tribute also to emission function and hence to the particle spectra.

• The cross-sections and collision rates in the hadronic gas are calculated in accordance with theUrQMD model.

• Initial conditions for hydrodynamic evolution are taken from Glauber or CGC approaches.

Switching to the transport code (UrQMD) is performed at the space-like hypersurface with essen-tially non-equilibrium hadron distribution functions calculated in hydro-kinetic approach. This es-sential extension of the model permits one to calculate the tails of hadron scatterings at low-densityfinal stage.With the model given, a reasonable description of transverse momentum spectra for several sortsof hadrons and pion HBT radii is achieved for top RHIC energy. The reproduction of recent ALICELHC femtoscopic results is also presented.

[1] Yu.M. Sinyukov, S.V. Akkelin and Y. Hama 2002 Phys. Rev. Lett. 89, 052301.[2] S. V. Akkelin, Y. Hama, Iu. A. Karpenko, and Yu. M. Sinyukov, Phys. Rev. C 78, 034906.[3] Iu.A. Karpenko, Yu.M. Sinyukov, Phys.Lett.B 688 (2010), 50-54.[4] Iu.A. Karpenko, Yu.M. Sinyukov, Phys.Rev.C 81 (2010), 054903.

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Non−Photonic Electron and Charged Hadron Azimuthal Corre-lation in p+p Collisions at

√s = 500 GeV in STAR

Author: Wei Li1

1 Shanghai Institute of Applied Physics


RHIC measurement on non-photonic electrons from heavy quark decays shows similar suppressionas light hadrons at high pT in central Au+Au collisions. However, the interpretation is complicatedby the combined contributions from charm and bottom decays. Non-photonic electron and chargedhadron azimuthal correlation has been used as a powerful tool to disentangle charm and bottomcontributions at

√s = 200 GeV up to pT ~ 9 GeV/c. Combining the non-photonic electron RAA and

the relative bottom decaycontribution in p + p collisions suggests the bottom decay electrons are also suppressed in centralAu+Au collisions.

We will report the preliminary results of non-photonic electron and charged hadron azimuthal cor-relation at midrapidity for 6.5<p_T<12.5 GeV/c in run 2009 p+p collisions at

√s=500 GeV at RHIC.

The correlation distributions are compared with PYTHIA simulations toextract the bottom relative contribution to non-photonic electrons. The comparison between 200GeV and 500 GeV results will deepen our understanding on the heavy flavor production at RHIC.

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Dielectron production in Au+Au collisions at √sNN = 39GeV atSTARAuthor: Patrick Huck1

1 CCNU + IKF + LBNL


During the beam energy scan in 2010 a wide range of beam energies has been explored for Au+Aucollisions using the STAR detector at RHIC. With minimum material budget in the tracking part ofthe detector this run is particularly suited for the investigation of virtual photons originating fromthe hot and dense medium created in heavy ion collisions. The completed installation of the STARtime-of-flight detector is a further distinctive feature which allows the particles’ velocity to be usedfor particle identification in addition to their energy loss in the time projection chamber. As electro-magnetic probes, dielectron pairs do not interact strongly with the medium and hence carry directinformation of its properties at the time of production. Thus, measurements of dielectron emissivityin heavy ion collisions provide an additional tool for the study of the quark gluon plasma. For acenter-of-mass energy of√sNN = 39GeV , 170M events have been taken. The poster presents thestatus of an ongoing dielectron analysis of this high statistics sample. It concentrates on particleidentification, background rejection and subtraction, and the reconstruction of dielectron pairs uptoMe+e−

inv = 3.5GeV /c2.

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QGP viscosity coefficients: from weak to strong couplingAuthor: Marcus Bluhm1

Co-authors: Burkhard Kampfer 2; Krzysztof Redlich 3

1 Laboratoire SUBATECH2 Helmholtz-Zentrum Dresden-Rossendorf & Technical University Dresden3 Wroclaw University


By means of high energy nuclear collisions, the properties, such asthe viscosity coefficients, of QCD matter under extreme conditionsare intended to be experimentally revealed. One remarkable resultfrom collisions at RHIC is that the produced hot matter is analmost ideal fluid, obeying the smallest shear viscosity to entropydensity ratio observed in nature. Employing an effective kinetictheory for quasiparticle excitations featuring dynamicallygenerated self-energies, we determine the temperature dependenceof the viscosity coefficients of deconfined strongly interactingmatter [1,2]. This knowledge may serve as input for thephenomenological description of heavy-ion collisions at LHC andRHIC.

Exhibiting the parametric dependencies known from perturbative QCDat large temperatures, the extrapolation of our results into thenon-perturbative region shows fairly nice quantitative agreementwith lattice QCD results in the case of a pure gluon plasma. Wefind a minimum in the specific shear viscosity and a rapid increaseof the specific bulk viscosity near the deconfinement transitiontemperature T_c. The ratio of bulk to shear viscosity comprises

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both, a quadratic dependence on the conformality measure at largetemperatures as known from pQCD as well as a linear dependencenear T_c as known from specific strongly coupled and nearlyconformal theories based on gauge/string duality [3]. Thus, theexploited framework provides a systematic interpolation betweenboth regimes of weak and strong coupling.

[1] M. Bluhm, B. Kampfer, K. Redlich, Nucl. Phys. A 830 (2009) 737C[2] M. Bluhm, B. Kampfer, K. Redlich, arXiv:1011.5634[3] M. Bluhm, B. Kampfer, K. Redlich, arXiv:1101.3072

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Equation of state of strongly interacting matter: spectra for ther-mal particles and intensity correlation of thermal photonsAuthor: Somnath De1

Co-authors: Dinesh Srivastava 1; Rupa Chatterjee 2

1 Variable Energy Cyclotron Centre2 University of Jyvaskyla


We find that an equation of state for hot hadronic matter consisting of all baryons having M < 2GeV and all mesons havingM < 1.5 GeV, along with Hagedorn resonances in thermal and chemicalequilibrium, matches rather smoothly with lattice equation of state (p4 action, Nτ = 8) for T up to≈ 200 MeV, when corrected for the finite volume of hadrons.Next we construct two equations of state for strongly interacting matter; one, HHL, in which theabove is matched to the lattice equation of state at T = 165 MeV and the other, HHB, where wematch it to a bag model equation of state with critical temperature Tc = 165MeV.We compare parti-cle spectra, thermal photon spectra and histories of evolution of the quark-gluon plasma produced inthe central collision of gold (lead) nuclei at RHIC (LHC) energies, considering ideal hydrodynamicalexpansion of the system. The particle and thermal photon spectra are seen to differ only marginally,for the two equations of state. The history of evolution shows differences in the evolution of tem-perature and radial velocity, as one might expect.We calculate intensity interferometry of thermal photons and find it to be quite distinct for the twoequations of state, especially for the outward correlation. The longitudinal correlation also shows adependence on the equation of state, though, to a smaller extent.Ref: J.Phys.G G37 (2010) 115004.

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Interference of thermal photons fromquark andhadronic phasesin relativistic collisions of heavy nucleiAuthor: Dinesh Srivastava1

Co-author: Rupa Chatterjee 2

1 Variable Energy Cyclotron Centre2 University of Jyvaskyla


We explore the intensity correlations for thermal photons having KT ≤ 2 GeV/c, for central colli-sions of heavy nuclei at RHIC and LHC energies. These photons get competing contributions from

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the quark and the hadronic phases. This competition gives rise to a unique structure, especially inthe outward correlation function, due to the interference between the photons from the two sources.The temporal separation of the two sources provides the life time of the system and their strengthsprovide the relative contribution of the two phases. The results are found to be quite sensitive to thequark-hadron phase transition temperature and the formation time of the plasma.Ref:Phys.Rev.C80:054914 (2009)

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Two freeze-out analysis of hadron yields and spectra at RHIC

Author: Kang Seog Lee1

Co-author: Suk Choi 1

1 Chonnam National University


With the two freeze-out model for the hadron production in the relativistic heavy-ion collisions,hadron ratios and their momentum spectra measured at RHIC are fitted. In this model the chemicalfreeze-out occurs earlier at higher temperature. In analyzing the hadron ratios, resonance contribu-tion has been carefully taken into account. After the chemical freeze-out the number of the thermalhadrons of each type is kept fixed as in-elastic collisions becomes less frequent, while the elastic col-lisions among the hadrons of the same species maintain the thermal equilibrium until the thermalfreeze-out. At the thermal freeze-out the chemical potentials for each hadron species are calcu-lated from the fixed number of thermal hadrons and the transverse momentum spectra of measuredhadrons are fitted with blast wave-type equation together with the resonance contribution.

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Measurements ofNon-photonic Electron Spectra andElliptic Flowin Au+Au Collisions from STAR at RHICAuthor: Xin Li1

1 STAR Collaboration


The dependence of parton energy loss on the space-time evolution of the QCDmedium is believed to be mostly responsible for the azimuthal angularanisotropy distribution of high transverse momentum (pT) particles innucleus-nucleus collisions. Simultaneous measurements of both the nuclearmodification factors and the elliptic flow parameter v2 can provide insightson parton energy loss mechanisms and space-time evolutions of the collidingsystem. Heavy quarks are particularly effective probes because their initialproduction can be reliably calculated from pQCD approaches and their finalstates reflect directly evolutions through the strongly interacting partonicmedium created in heavy ion collisions. We will present the STARnon-photonic electron (NPE) measurements at high pT from p+p and Au+Aucollisions. The data were taken during run 2009 and run 2010, whereunprecedented amount of data have been collected with detectorconfigurations for minimum photonic conversion background. Both the nuclearmodification factors and the v2 measurements will be reported as a functionof pT and collision centralities. Comparisons with theoretical model

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calculations and possible constraints on properties of the partonic mediumwill be discussed.

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Effects of final state interactions on charge separation in relativis-tic heavy ion collisionsAuthors: Bin Zhang1; Guo-Liang Ma2

1 Arkansas State University2 Shanghai Institute of Applied Physics


Charge separation is an important consequence of the Chiral Magnetic Effect. Within the frameworkof a multi-phase transport model, the effects of final state interactions on initial charge separationare studied. We demonstrate that charge separation can be significantly reduced by the evolution oftheQuark-Gluon Plasma produced in relativistic heavy ion collisions. Hadronization and resonancedecay can also affect charge separation. Moreover, our results show that the Chiral Magnetic Effectleads to the modification of the relation between the charge azimuthal correlation and the ellipticflow that is expected from transverse momentum conservation only. The transverse momentum andpseudorapidity dependences of, and the effects of background on the charge azimuthal correlationare also discussed.

Reference:Effects of final state interactions on charge separation in relativistic heavy ion collisions, Guo-LiangMa, Bin Zhang, arXiv:1101.1701 [nucl-th]

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Nucleonmass generated from confinement and a dynamic gener-ation of the quark massesAuthor: Jean-Christophe CAILLON1

1 CENBG


We have built the nucleon by taking into account explicitly both confinement like in an MIT bagmodel and a dynamic generation of the quark masses in a Nambu Jona Lasinio model.Therefore, we have supposed a QCD vacuum modified in a cavity and thus a modified quark con-densate coming from the presence of three valence quarks in this cavity. Quarks acquire theirmasses through their interaction with this modified quark condensate which is itself determinedself-consistently by the equilibrium condition for the bag : the outward pressure due to both themotion of three quarks and the modified vacuum in the nucleon must be counterbalanced by theinward pressure of the vacuum outside the bag.We are able to pass continuously from a nucleon description in a pureMIT bagmodel to a descriptionusing constituent quark masses determined in an NJL model.

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Beauty in the QGP from the lattice

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Author: Jon-Ivar Skullerud1

Co-authors: Chris Allton 2; Don Sinclair 3; Gert Aarts 2; Maria-Paola Lombardo 4; Mehmet Bugrahan Oktay 5;Seyong Kim 6; Sinead Ryan 7

1 National University of Ireland Maynooth2 Swansea University3 Argonne National Laboratory4 INFN Frascati5 University of Utah6 Sejong University7 Trinity College Dublin


We study the temperature dependence of bottomonium for temperatures in the range 0.4Tc < T <2.1Tc, using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simula-tions forNf = 2 light flavors on a highly anisotropic lattice. We find that theΥ is insensitive to thetemperature in this range, while the χb propagators show a crossover from the exponential decaycharacterizing the hadronic phase to a power-law behaviour consistent with nearly-free dynamicsat T ≃ 2Tc.

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Dimuon radiation at the CERN SPS within a hybrid evolutionmodelAuthor: Elvira Santini1


1 Goethe Universität Frankfurt2 Goethe Universität Frankfurt and Frankfurt Institute for Advanced Studies (FIAS)


In this talk I discuss dilepton emission from hot and dense matter created in heavy-ion collisions andpresent results on dimuon invariant and transverse mass spectra obtained using a hybrid approachbased on the UrQMD transport model with an intermediate hydrodynamic stage for the modelingof heavy-ion dynamics.During the hydrodynamic stage, the production of lepton pairs is described by radiation rates for astrongly interacting medium in thermal equilibrium. In the low mass region, hadronic thermal emis-sion is evaluated assuming vector meson dominance including in-medium modifications of the rhomeson spectral function through scattering from nucleons and pions in the heat bath. In the interme-diate mass region, the hadronic rate is essentially determined by multi-pion annihilation processes.Emission from quark-antiquark annihilation in the quark gluon plasma is taken into account as well.When the system is sufficiently dilute, the hydrodynamic description breaks down and a transitionto a final cascade stage is performed. In this stage dimuon emission is evaluated as commonly donein transport models. Focusing on the enhancement with respect to the contribution from long-livedhadron decays after freezout observed at the SPS in the low mass region of the dilepton spectra,the relative importance of the different thermal contributions and of the two dynamical stages isdiscussed.

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D+ analysis in Pb-Pb collisions at √ sN N = 2.76 TeV at the LHCwith ALICE.

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Author: Giacomo Ortona1

1 Universita & INFN, Torino


A Large Ion Collider Experiment (ALICE) is one of the four experiments at the Large Hadron Col-lider (LHC), and the only one mainly dedicated to ultra relativistic heavy ion collisions, in order toinvestigate the properties of the high-density state of QCDmatter produced in such events. The firstPb-Pb collisions at a centre of mass energy of √s = 2.76 TeV for nucleon pair were delivered by LHCin November 2010.In Pb-Pb collisions heavy quarks are regarded as sensitive probes ofthe interaction dynamics between the parton and the medium producedin such collisions as they are produced on a very short time scale and they follow all the evolutionof the medium. At the energies available at LHC charm is produced abundantly and therefore it ispossible to study the production of charm with high statistics. In this poster the analysis for D+ →K − π + π + reconstruction in Pb-Pb collisions at ALICE will be presented, along with the prospectsfor D+ elliptic flow and energy loss measurements.

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Next-to-leading order analysis of inclusive jet, tagged jet and di-jet production in PbPb collisions at the LHCAuthor: Ivan Vitev1

1 Los Alamos National Laboratory


Jets physics is an important new area of active research at RHIC and at the LHC that paves the wayfor novel tests of QCD multi-parton dynamics in heavy-ion reactions. At present, perturbative QCDcalculations of hard probes in “elementary” nucleon-nucleon reactions can be consistently combinedwith the effects of the nuclear medium up to next-to-leading order. While such accuracy is desir-able for leading particle tomography, it is absolutely essential for the new jet observables. Withthis motivation, we present results and predictions at NLO for the recent LHC lead-lead (Pb+Pb)run at a center-of-mass energy of 2.76 TeV per nucleon-nucleon pair. Specifically, we focus on thesuppression the single and double inclusive jet cross sections and demonstrate how the di-jet asym-metry, recently measured by ATLAS and CMS, can be related to these general results. The case ofjets tagged by an electroweak boson is exemplified by the Z0+jet channel. We predict a signaturetransition from enhancement to suppression of the tagged jet reflective of the medium-induced mod-ification of parton showers. We also present NLO results relevant to the inclusive Z0 data obtainedby the CMS collaboration. Our analysis includes not only final-state inelastic parton interactions inthe QGP, but also initial-state cold nuclear matter effects and non-perturbative hadronization cor-rections. Finally, we clarify the relation between the suppression of inclusive jets, tagged jets anddi-jets and the quenching of inclusive particles on the example of the recent ALICE neutral pionattenuation data. We conclude by discussing future directions and effective theories of QCD thatcan help improve the accuracy of the theoretical tools for jet tomography.

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Reconstruction of Ds mesons in the ALICE Experiment at LHC

Authors: Gian Michele Innocenti1; Sadhana Dash1


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Open Charm mesons produced in relativistic nuclear reactions are among the most direct probesto investigate the medium produced in these collisions. Ds mesons act as an useful probe to studyhadronization mechanism in heavy ion collisions. The study on exclusive reconstruction of the Dsmesons via the decaychannel (Ds->KKpi ) for p+p collisions at 7 TeV is presented. Themeasurement will allow us to studyratios of charmed-strange mesons to other D mesons and will act as baseline reference for the Dsmeasurement in heavy-ion collisions.The ALICE experiment at the LHC is designed to perform such measurements at mid-rapidity bymeans of its barrel tracking detectors. The barrel tracking detectors provide the momentum infor-mation and the particle identification of thecharged particles together with an accurate measurement of the primary and secondary vertexpositions. The study on selection cuts to optimize the combinatorial background rejection willbe described. The Ds signal in the KKpi invariant mass distribution for various pT bins will beshown.

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Dissipative dynamics of highly anisotropic plasmasAuthor: Mauricio Martinez Guerrero1

Co-author: Michael Strickland 2

1 FIAS2 Gettysburg College


We present a method to improve the description of 0+1 dimensional boostinvariant dissipative dynamics in the presence of large momentum-spaceanisotropies. Instead of using the canonical hydrodynamical expansion of the distribution functionaround an isotropic equilibrium state, we expand around a state which is anisotropic in momentumspace and parameterize this state in terms of three proper-time and spatial-rapidity dependent pa-rameters. At leading order the result obtained is two coupled hydro-like differential equations for themomentum-space anisotropy and typical momentum of the degrees of freedom. Within this frame-work, we get both the ideal hydrodynamic and free streaming expansion as asymptotic limits. Inaddition, we show that when linearized the differential equations reduce to 2nd order Israel-Stewartviscous hydrodynamics. Finally, we make quantitative comparisons of the evolution of the pressureanisotropy within our approach and 2nd order viscous hydrodynamics in both the strongand weak coupling limits. We make quantitative comparisons of theevolution of the pressure anisotropy within our approach and 2nd orderviscous hydrodynamics in both the strong and weak coupling limits.Finally, we comment about the generalization of this framework tonon-boost invariant expansion.


Event anisotropy v2 of identifiedhadrons and light nuclei inAu+Aucollisions at √sNN = 7.7, 11.5 and 39 GeV with STAR

Author: Alexander Schmah1

1 Lawrence Berkeley National Lab


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The main goal of the RHIC Beam Energy Scan (BES) is the explorationof the QCD phase diagram in the region of a possible phasetransition between the Quark Gluon Plasma (QGP) and the hadron gasphase. In the year 2010 the first part of the BES program wassuccessfully accomplished by recording data from Au+Au collisionsat √sNN = 7.7, 11.5 and 39 GeV. The second harmonic(v2) of the azimuthal particle distribution relative to the reaction planewas found to be one of the most important observables tostudy the underlying dynamics in the early stage of the collisions.The number-of-constituent quark (NCQ) scaling of v2 isinterpreted as a signature of deconfinement and existence of the QGP phase.At the lower energies studied it was expected to see a change in thisscaling behaviour as the role of the QGP phase should diminish.

We present v2 measurements at all three beam energies foridentified hadrons (π,K , K0

s , p, ϕ, Λ,Ξ) and light nuclei (d and 3He) as a function of pT forvarious collision centralities. The measured nuclei v2 arecompared to the proton v2 and results from a dynamical coalescencemodel calculation, while the NCQ scaling is tested using all identified hadrons.For the first time, a significant difference in v2 between baryons andanti-baryons is observed. The difference increaseswith decreasing center-of-mass energy.

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Centrality dependence of the Υ Nuclear Modification Factor at√sNN = 200 GeV measured with STAR

Author: Rosi Reed1

1 STAR

Suppression of quarkonia in heavy ion collisions with respect to proton-proton collisions was hy-pothesized to be a signature of the Quark Gluon Plasma (QGP). However, effects such as the sta-tistical recombination of heavy flavor quark-antiquark pairs or co-mover absorption can also af-fect quarkonia production. For the bottomonium states these competing effects are expected to besmaller than for the charmonium states. Lattice calculations show that quantifying the suppressionof an entire family of quarkonium mesons can give us a model dependent measurement of the tem-perature of the matter produced in heavy ion collisions. For the Υ family, calculations indicate thatthe Υ(1S) state should not be suppressed at

√(s) = 200 GeV, which would give a standard candle

that the Υ(2S) and Υ(3S) states can be compared to. The suppression of quarkonia can be quan-tified by calculating the nuclear modification factor RAA, which is the ratio of production in p+pscaled by the number of binary collisions to the production in Au+Au collisions.

We will present results for mid-rapidity Υ(1S + 2S + 3S) production in p+p, d+Au and Au+Aucollisions at √sNN = 200 GeV. These results will be combined into RdA and RAA and compared totheoretical QCD calculations. The centrality dependence of RAA will be shown for the combinedΥ(1S+2S+3S) yield as well as for the /Upsilon(1S) yield. The invariant yield versus transversemomentum in Au+Au collisions will also be discussed.

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Investigating jet and non-jet contributions to long range pseudo-rapidity correlations in di-hadronmeasurements fromSTAR.

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Author: Chanaka De Silva1

1 University of Houston


Two particle number correlations in relative azimuth and pseudo-rapidity (∆ϕ, ∆η) develop novelfeatures in heavy ion collisions at 200 GeV when compared to p+p results at the same energy.

Earlier STAR results have shown a ∆η elongated structure for the small ∆ϕ angles (on the same-side) and the development of significant deformations at ∆ϕaproxπ (on the away-side). In this talk we will present new results from such correlation analysisthat show unambiguously formation of a double-hump structure on the away side in raw correlationmeasured in very central Au+Au collisions for intermediate pT (2<pT<5GeV/c) particles.

We carry out systematic investigation of the same- and away-side features by varying the eventcentrality and kinematic selection for 200GeV Cu+Cu and Au+Au collisions. To characterize theobserved correlation structure we fit the data with a multi-component model that includes a sameside Gaussian and higher order Fourier moments (vn; n = 1,2,3,4). The impact of including the thirdFourier moment in the fit on the elongated same-side structure and the second Fourier moment(related to the elliptic flow strength) is discussed.

Finally we compare our data to theoretical expectations based on CGC initial conditions [1], [2],initial density fluctuations [3] and pQCD [4]. We conclude that, within the studied model, the same-side eta elongated structure is consistent with a coexistence of jet and non-jet contributions.

[1]. Gavin, McLerran and Moschelli: Phys.Rev.C79:051902, 2009[2]. Moschelli and Gavin: Nucl.Phys.A836: 43-58, 2010[3]. Alver and Roland: Phys.Rev.C81:054905, 2010[4]. T. Trainor and D. Kettler: Phys.Rev.C.83:034903, 2011

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Leading hadron PID effects in di-hadron angular correlations inSTARAuthor: Kolja Kauder1

1 University of Illinois at Chicago


Hard scatterings of partons provide a valuable colored probe of thestrongly-coupled medium created in ultra-relativistic heavy ioncollisions. These hard scatterings can be studied by means of angularcorrelations of charged hadrons with respect to a high transversemomentum trigger particle. Several recent two-particle correlationstudies indicate that A+A collision dynamics evolve significantlywith collision centrality. They specifically reveal the presence ofunexpected strong away-side deformation and the development of along-range “ridge” in correlation measured as a function of∆η vs ∆ϕ. The detailed physics mechanismsresponsible for these features however remain under activeinvestigation.

We will present preliminary results of a new di-hadron correlationanalysis, measured as a function of ∆ϕ vs ∆η,for identified high-pT triggers from the high-statistics 200 GeV Au+Audata sample collected by the STAR experiment at RHIC during Run-10.The relativistic rise of the ionization energy loss dependence of

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particles measured in the STAR TPC is used to obtain a statisticalseparation of charged pions, kaons, and protons. The ∆ϕ vs∆η correlations measured in this work extend earliermeasurements of azimuthal correlations (in ∆ϕ only) withidentified hadron triggers, which, admittedly with largeuncertainties, reported no significant dependence on a leading hadronidentity. The added ∆η dimension and improved statisticsreveal a rich set of new features: the near-side (|∆ϕ| < 1)associated hadron distributions with respect to high-pT pion, kaonand proton triggers exhibit distinctly different featuresfor both “ridge” (large ∆η and small ∆ϕ) and“jet-like” (|∆ϕ| < 0.7 excluding the ridge) particles.We will discuss the implications of these results in the context ofthe existing models and possible connection of the leading hadron IDwith the color-charge and/or flavor of a hard-scattered parton.


Charge fluctuations in chiral models and the QCD phase transi-tionAuthor: Vladimir Skokov1

Co-authors: Bengt Friman 1; Krzysztof Redlich 2

1 GSI, Darmstadt, Germany2 Wroclaw University, Poland


Fluctuations of conserved charges are key probes of the chiralphase transition in a QCD medium. Of particular phenomenological importance are studies of suchfluctuations at finite baryon density. A valuable tool for assessing critical fluctuations and the ther-modynamics at non-vanishing baryon density is provided by effective chiral models.

We consider the Polyakov loop-extended two flavors chiral quark–meson model (PQM) and dis-cuss critical phenomena related with the spontaneous breaking of chiral symmetry. The model isexplored beyond the mean-field approximation in the functional renormalisation group (FRG) ap-proach.

We formulate and solve the renormalization group flow equation for the scale-dependent thermody-namic potential in the presence of the gluonic background field at finite temperature and density [1]and determine the phase diagram of the PQMmodel in the FRG approach [2]. We also consider prop-erties of the net-quark number density fluctuations as well as their higher cumulants [3] and discussthe influence of nonperturbative effects on their properties near the chiral crossover transition. Withincreasing net-quark number density, the higher order cumulants show a strong dependence on thechiral crossover transition. This is illustrated by exploring the ratios of moments of net-baryon num-ber and electric charge fluctuations. We discuss their role as probes of deconfinement and the chiralphase transition in heavy ion collisions at RHIC and LHC.

[1] V. Skokov, B. Stokic, B. Friman, K. Redlich, Phys.Rev.C82:015206,2010.[2] V. Skokov, B. Friman, K. Redlich, arXiv:1008.4570[3] B. Friman, F. Karsch, K. Redlich, V. Skokov, arXiv:1103.3511

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Roles of Axial Anomaly on Neutral Strongly Interacting Matter

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—- New Critical Points at Low Temperature and the Absence ofChromomagnetic Instabilty —-Authors: Teiji Kunihiro1; zhao zhang2

1 Kyoto University, Japan2 North China Electric Power University,China


We investigate effects of the axial anomaly termwith a chiral-diquark coupling on the phase diagramwithin a two-plus-one-flavor Nambu-Jona-Lasinio (NJL) model under the charge-neutrality and β-equilibrium constraints. We find that when such constraints are imposed, the new anomaly termplays a quite similar role as the vector interaction does on the phase diagram, which the presentauthors clarified in a previous work. Thus, there appear several types of phase structures withmultiple critical points at low temperature T , although such phase diagrams with low-T criticalpoint(s) are never realized without these constraints even within the same model Lagrangian. Thisdrastic change is attributed to an enhanced interplay between the chiral and diquark condensates dueto the anomaly term at finite temperature; the u-d diquark coupling is strengthened by the relativelylarge chiral condensate of the strange quark through the anomaly term, which in turn definitely leadsto the abnormal behavior of the diquark condensate at finite T , inherent to the asymmetric quarkmatter. We also show that the chromomagnetic instability of the neutral asymmetric homogenoustwo-flavor color superconducting(2CSC) phase is suppressed and can be even completely cured bythe enhanced diquark coupling due to the anomaly term and/or by the vector interaction

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J/psi analysis in proton+proton at 7 TeV in the ALICE muon spec-trometer using a pT - y correction method.Author: Bruno Alexandre Boyer1

1 Institut de Physique Nucleaire (IPN)-Universite de Paris-Sud (Pa


ALICE (A Large Ion Collider Experiment) is the LHC experiment dedicated to the study of theQuarkGluon Plasma (QGP) using heavy-ion collisions. Heavy quarkonium measurements in pp collisionsare very important to constraint the different models available and as a reference for heavy ioncollisions. Acceptance x efficiency corrections are a fundamental step of the analysis in order toextract the cross-section. In this poster, I will present a J/psi inclusive analysis in the diumon channelon a large sample of pp data at 7 TeV. Acceptance and efficiency corrections will be performed as afunction of the transverse momentum and rapidity on the J/psi.

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Search for theQCDCritical Point: HigherMoments ofNet-proton,Net-charge Multiplicity Distributions from the RHIC Beam En-ergy ScanAuthor: Xiaofeng Luo1

1 University of Science and Technology of China (USTC); Lawrence Berkeley National Lab (LBNL)


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One of the main goals of the RHIC Beam Energy Scan (BES) program is to search for the QCD criticalpoint and the phase boundary in the QCD phase diagram. Due to high sensitivity to correlationlength and direct connection to thermodynamical susceptibilities calculated in Lattice QCD and theHadron Resonance Gas (HRG) model, higher moments of event-by-event net-proton and net-chargemultiplicity distributions are used to search for the QCD critical point.

In this talk, we will present various moments (variance (σ2), skewness (S), kurtosis (κ)) and momentproducts (κσ2 and Sσ) of the net-proton, net-charge multiplicity distributions measured by STARdetector at RHIC. The moment products κσ2 and Sσ of net-proton (net-charge) distributions arerelated to baryon (charge) number susceptibility ratios and are volume independent. The mix-ratioof the moments of proton and kaonmultiplicities, which are predicted to be without any dependenceon model parameters including the correlation length, will be also presented to establish the baselines. The data presented in this talk will include themeasurements from Au+Au collisions at energies √

sNN = 7.7, 11.5 and 39 GeV collected in theyear 2010 and √

sNN = 200 GeV in the year 2004. Deviations from HRG models for κσ2 and Sσ ofnet-proton and net-charge distributions are observed for BES energies.

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Multihadron production in hadronic and nuclear collisionsAuthor: Edward Sarkisyan-Grinbaum1

Co-author: Alexander Sakharov 2

1 CERN2 Wayne University


The energy-dependence of charged particle mean multiplicity and pseudorapidity density at midra-pidity measured in nucleus-nucleus and (anti)proton-proton collisions are studied in the entire avail-able energy range. The study is performed using amodel, which considers the multiparticle production process according to the dissipating energy ofthe participants and their types, namely a combination of the constituent quark picture togetherwithLandau relativistic hydrodynamics. The model reveals interrelations between the variables understudy measured in nucleus-nucleus and nucleon-nucleon collisions. Measurements in nuclear reac-tions are shown to be well reproduced by the measurements in pp/pbarp interactions up to RHICenergies. Heavy-ion measurements at the LHC are discussed.

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Prospects for charm RAA in PbPb collisions at LHC via D0->Kpireconstruction in ALICEAuthor: Davide Caffarri1

1 Universita degli Studi di Padova- INFN Padova & CERN

The main goal of the ALICE experiment is the investigation of the properties of strongly-interactingmatter in a very high density deconfined state, that is thought to be formed in Pb-Pb collisions atLHC. The ALICE experiment has collected Pb-Pb data at sqrts_NN = 2.76 TeV and p-p data both atsqrts = 7 and 2.76 TeV.In Pb-Pb collisions, heavy quarks are sensitive probes to test the medium properties, as they areformed at shorter time scale with respect to the deconfines state. These quarks can interact with themedium via collisional and radiative energy loss. The nuclear modification factor (RAA), obtained

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comparing p-p and Pb-Pb pT-differential distributions, allows to measure the effect of in-mediumenergy loss.We will present the prospects for the first open charm energy loss measurement, considering theD0 in Kπ decay channel. The reconstruction of this decay channel exploits the excellent tracking,vertexing and particle identification capabilities of the ALICE experiment.


STAR science for the coming decadeAuthor: Carl Gagliardi1

1 STAR Collaboration


The STAR Collaboration has identified eight key questions that will drive RHIC science during thecoming decade, six of which involve ultrarelativistic heavy-ion collisions. What is the nature ofthe initial state in nuclear collisions? What are the properties of the strongly-coupled system pro-duced at RHIC, and how does it thermalize? Are the interactions of energetic partons with QCDmatter characterized by weak or strong coupling, and what is the detailed mechanism for partonicenergy loss? Where is the QCD critical point and the associated first-order phase transition line?Can we strengthen current evidence for novel symmetries in QCD matter and open new avenues?What exotic particles are created at RHIC? The STAR detector, with its large acceptance tracking,calorimetry, and particle identification, is an ideal tool to explore these questions. Complete an-swers nonetheless will require detector upgrades. Near-term upgrades, including the Heavy FlavorTracker and Muon Telescope Detector, will enable a rich program of heavy flavor physics. Upgradesto the forward region will enable detailed studies of the partonic structure of nuclei and the onset ofgluon saturation. An additional suite of upgrades during the latter part of the decade will positionSTAR to make crucial measurements in e+p and e+A collisions during the early phase of eRHIC.Thetalk will provide an overview of this STAR decadal plan.

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Development of the CBM RICH detectorAuthor: Tariq Mahmoud1

Co-author: RICH Collaboration CBM 2

1 Universität Gießen2 –


The Compressed Baryonic Matter (CBM) experiment is the future heavy-ion experiment at FAIRbeing designed to explore the intermediate range of the QCD phase diagram in a beam energy inter-val of 10-45 AGeV. With its physics program CBM will investigate the properties of dense baryonicmatter and the expected phase transition between hadronic and partonic matter. Among the keyobservables are low-mass vector mesons and charmonium decaying into lepton pairs. In CBM, elec-trons with energies lower than 8 GeV/c will be identified through a RICH detector being developedat several laboratories. In addition the detector will improve the kaon/pion separation at momentahigher than 4 GeV/c.

The proposed concept of the RICH detector foresees CO2 as radiator gas, spherical glass mirrorsreflecting the Cerenkov radiation on an array of Multianode Photomultipliers (MAPMTs) as photodetectors.

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CO2 has been chosen because it has a Lorenz factor, gth, of 33.3, a radiation length of 183 m and apion momentum threshold for Cerenkov light production of 4.65 GeV/c, it represents a very goodcompromise to fulfill the CBM RICH requirements.The mirror system will be of approximately 11.8 m² with a curvature radius of 3 m and a thicknessof 6 mm. For the reflective coating Al+MgF2 are foreseen. In order to cover a spherical mirror wallwith a radius of 3 m, square mirror tiles of approximately 40×40cm² will be used.Regarding the photo detector investigations indicated that the 64 channel HamamatsuH8500MAPMTis one of the most promising candidates for the CBM RICH. The main criteria for the readout of thisMAPMT are the high interaction rates (up to 10MHz) and the challenging high level triggers in CBM.To cope with these facts a self triggered readout electronics is foreseen. The Front End Electronics(FEE) will be based on a further development of the so called n-XYTER chip which was developedfor the readout of silicon detectors. The chip offers 128 channels at a readout speed of 32 MHz. Asan intermediate solution the high gain of the MAPMT is currently matched to the existing chip viaa charge attenuator board.

These components were successfully tested in laboratories and in several test beams. Single photoncounting and Cerenkov light detection confirmed the suitability of the FEE and MAPMT setup. Thetests also show that uncorrelated noise can be well separated from the signal using available timinginformation. The usage of wavelength shifter films in order to enhance the quantum efficiency of theMAPMT for wavelengths below 300 nm is investigated. An industrial provider for mirror prototypeswith promising surface homogeneity and reflectivity has been found.

The concept of the RICH detector as well as results of several tests will be presented. They are valu-able experience for the preparation of a full scale RICH prototype setup currently under constructionand to be tested at CERN in fall 2011.

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Dynamical equilibration of strongly-interacting ’infinite’ partonmatter within a Parton-Hadron-String Dynamics (PHSD) trans-port approachAuthor: Vitalii Ozvenchuk1

1 FIAS


I study the kinetic and chemical equilibration in ‘infinite’ parton

matter within the Parton-Hadron-String Dynamics transport approach,

which is based on a dynamical quasiparticle model for partons

matched to reproduce lattice-QCD results – including the partonic

equation of state – in thermodynamic equilibrium. The ‘infinite’

matter is simulated within a cubic box with periodic boundary

conditions initialized at different energy density. Different

thermodynamical distributions of the strongly-interacting

quark-gluon plasma (sQGP) are addressed and discussed.


Jets in QCD media: from color coherence to decoherence

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Author: Yacine Mehtar-Tani1

Co-authors: Carlos Salgado 1; Konrad Tywoniuk 2

1 University of Santiago de Compostela2 Lund University


Jet physics in hadronic collisions is one of the major achievements of perturbative QCD. However,a complete theory of jets in a hot and dense partonic environment remains to be developed. Sucha theory is needed in Heavy-Ion Collisions (HIC), at RHIC and now at the LHC, in order to have aclean access to the properties of the Quark-Gluon Plasma (QGP).

To this end, we have investigated mediummodification of the radiation pattern of a quark-antiquarkantenna traversing a dense medium in order to understand how the QGP alters color coherencewhich is an important feature of the intRAjet structure in vacuum. In contrast to gluon radiation invacuum, and unexpectedly, we find a strict geometrical separation between in-vacuum and medium-induced gluon radiation. Also, a soft logarithmic divergence appears pointing to the possibility ofresuming multiple gluon branching in the cascade. Moreover, in the case of an opaque medium nearthe unitarity bound, a simple and intuitive physical picture arises : the interaction with the QGPleads to the gradual decoherence of the pair yielding a universal radiation pattern which does notdepend on the initial color configuration of the antenna.These results are in qualitative agreement with the recent ATLAS and CMS data and provide a start-ing point for further studies on in-medium jet modification.

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Heavy-flavor dynamics innucleus-nucleus collisions: fromRHICto LHCAuthors: AlfredoMolinari1; Andrea Beraudo2; ArturoDe Pace3; Francesco Prino3; MarcoMonteno3; Marzia Nardi3;Wanda Maria Alberico1

1 Dip.Fis.Teor.Univ.Torino/INFN Torino2 Centro Fermi/CERN3 INFN Torino


The understanding of the heavy-quark dynamics in nucleus-nucleus collisions, so far possible atRHIC only through the inclusive measurement of electron spectra from c and b decays, is becomingnow accessible at LHC also through the exclusive reconstruction of open-charm hadrons, thus pro-viding a richer physical information useful to discriminate among different theoretical models.A complete setup to study heavy-flavor observables in pp and AA collisions was recently developedby us: in the latter case the presence of a hot fireball leads to a modification of the final p_T-spectra.More specifically, the propagation of c and b quarks in the plasma (whose evolution is supposed tobe described by relativistic hydrodynamics) is followed by solving the relativistic Langevin equationwithin a picture of multiple uncorrelated random collisions. The relevant heavy-quark transportcoefficients are given a microscopic evaluation within the Hard Thermal Loop approximation, sup-plemented by a kinetic pQCD calculation for hard collisions.The results obtained with this approach turned out to be in reasonableagreement with the experimental data obtained at RHIC, in particularfor the R_AA of non-photonic electrons.Here we extend the above study to the LHC case, at the current center-of-mass energy of 2.76 TeV.Thefirst data on primary charged particle density obtained by theALICE collaboration (dN_ch/deta~1600in central PbPb collisions) allow to provide an estimate of the initial conditions of the hydrodynam-ical evolution of the background medium. First results for the spectra, the R_AA and v_2 of open-charm hadrons and non-photonic single-electrons will be presented.

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Dissipative hydrodynamics for relativistic multi-component sys-temsAuthor: Andrej El1

Co-authors: Carsten Greiner 1; Francesco Lauciello 1; Ioannis Bouras 1; Zhe Xu 1

1 University of Frankfurt


Novel set of second-order dissipative hydrodynamic equations for shear stress tensor of eachcomponent of a multi-component mixture is derived using the entropy principle [1]. Summationoverthe equations for all components leads to an effective relaxation-type one-component equation forthe total system. In this equation the effective shear viscosity (or alternatively the η/sratio) of the whole system is related to the partial shear pressures and cannot be considered as anexternal parameter. We demonstrate that in order to describe hydrodynamic behaviour of amulti-component system as a whole it is essential to solve hydrodynamic equations for eachcomponent, instead of treating a mixture as an effective one-component system with the freeparameters η/s and initial time [1]. This conclusion is confirmed by comparisons of solutionsof the new hydrodynamic equationswith results of kinetic transport simulations, which demonstratea very good agreement between the two approches. Thus, extractions of the η/s value of the QGPat RHIC and LHC have to be reexamined. We apply the obtained multi-component hydrodynamicequationsto quantify the dissipative effects on quark and gluon spectra, which are relevant for coalescenceand recombination models of hadronization.

[1] A. El, I. Bouras, F. Lauciello, Z. Xu and C. GreinerarXiv:1103.4038v1 (Submitted to PRL)

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Linear confinement and phase transitions in holographic QCD

Author: Mohammed Mia1

Co-authors: Charles Gale 2; Keshav Dasgupta 2; Sangyong Jeon 2

1 Columbia University2 McGill University


We study linear confinement of quarks in a class of large N gauge theories using gravity duals thatcapture the logarithmic runnings of the coupling constants in the IR and strongly coupled asymptoticconformal behavior in the UV. First we classify the most general dual gravity that describes linearconfinement of quarks at zero temperature and then show that at higher temperatures, quarks mustdeconfine. Using the gravity description, we also compute energy and pressure density of the gaugetheory plasma and observe a rapid change as temperature is altered, indicating a phase transition.Finally we estimate the critical temperature and discuss how to analyze phase transitions in nuclearmatter using holography.

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From RHIC to LHC: heavy quarks and J/psi in a partonic trans-port modelAuthor: Jan Uphoff1

Co-authors: Carsten Greiner 1; Oliver Fochler 1; Zhe Xu 2

1 Goethe University Frankfurt2 Frankfurt Institute for Advanced Studies


Heavy quark and J/psi production as well as their space-time evolution are studied in transportsimulations of heavy-ion collisions at RHIC and LHC. In the partonic transport model BoltzmannApproach of MultiParton Scatterings (BAMPS) heavy quarks can be produced in initial hard partonscatterings or during the evolution of the quark-gluon plasma. Subsequently, they interact with themedium via binary scatterings with a running coupling and a more precise Debye screening which isderived from hard thermal loop calculations. We present results on the elliptic flow and the nuclearmodification factor of heavy quarks, compare them to available data and estimate the impact ofradiative corrections quantitatively. Furthermore, results on J/psi suppression at forward and mid-rapidity are reported for central and non-central collisions. For this, we investigate cold nuclearmatter effects and the dissociation as well as regeneration of J/psi in the quark-gluon plasma.

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Percolation of Color Sources and the Equation of State of QGP incentral Au-Au collisions at √sNN =200 GeV

Author: Rolf scharenberg1

1 Purdue University


The Color String Percolation Model (CSPM)[1] is used to determine the equation of state (EOS)of the Quark-Gluon Plasma (QGP) produced in central Au-Au collisions at √sNN = 200 A GeVusing STAR data at RHIC.When the initial density of interacting colored strings exceeds the 2Dpercolation threshold a cluster is formed, which defines the onset of color deconfinement. Theseinteractions also produce fluctuations in the string tension which transforms the Schwinger particle(gluon) production mechanism into a maximum entropy thermal distribution analogous to QCDHawking-Unruh radiation. The single string tension is determined by identifying the known valueof the universal hadron limiting temperature Tc = 167.7 ± 2.6 MeV with the CSPM temperatureat the critical percolation threshold parameter ξc =1.2. At mid-rapidity the initial Bjorken energydensity and the initial temperature determine the number of degrees of freedom consistent with theformation of a∼ 2+1 flavor QGP. An analytic expression for the equation of state, the sound velocityC2

s (ξ) is obtained in CSPM. The CSPM C2s (ξ) and the bulk thermodynamic values energy density

ε/T 4 and entropy density s/T 3 are inexcellent agreement in the phase transition region with recent lattice QCD simulations (LQCD) bythe HotQCD Collaboration [2].

[1]. M. A. Braun, C. Pajares, Eu. Phys. J. C16, 349 (2000).[2].A. Bazavov et al., Phys. Rev. D80, 014504 (2009).

Heavy Flavors / 273

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Open charm hadron measurement in pp and Au+Au collisions at√s = 200 GeV in STAR

Author: Yifei Zhang1



Heavy quark production in elementary particle collisions are expected tobe calculable in pQCD. In relativistic heavy ion collisions, heavyquarks are believed to be an ideal probe to study the properties of thecreated QCD medium. Early RHIC measurements were carried out mostly viasemi-leptonic decay electrons. There are limitations in the electronapproach: the charm hadron and electron kinematics are only weaklycorrelated due to the decay, and measured electrons have mixedcontributions from various charm/bottom hadrons. Thus direct measurementof charm hadrons via hadronic decays is crucial to better understandcharm-medium interactions at RHIC.

In this talk, we will present the STAR preliminary results of D0 and D*in year 2009 p+p and D0 in year 2010 Au+Au collisions via hadronic decayscovering pT from 0.4 to 6 GeV/c in mid-rapidity |y|<1 at√sNN = 200 GeV. Newly completed full barrel Time-Of-Flight

detector was used in the analysis to improve the daughter hadronidentification. The charm production pT cross section in p+pcollisions will be compared with pQCD calculations. The nuclearmodification factors as a function of the collision centrality will bepresented to discuss the number of binary collisions scaling of charmtotal cross-section. The behavior of D-meson freeze-out properties inAu+Au collisions will be compared with those of light and multi-strangehadrons. Preliminary results of the D0 decay vertex reconstruction inAu+Au collisions at √sNN = 200 GeV from RHIC year 2007 using thesilicon detectors of the STAR experiment will also be presented.

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A High Level Online Tracking Trigger for the STAR experimentat RHICAuthor: Aihong Tang1



In order to utilize the high luminosity provided by RHIC and theenhanced data acquisition capability of STAR, a High Level onlinetracking Trigger (HLT) is being developed to effectively study theproperties of the QGP created at RHIC. Based on the fast tracking andevent assembling, the STAR HLT can select events of great physicsinterest online, which will reduce the rate to tape as well as thetime of offline processing. In year 2010, the HLT has successfullyselected events for J/psi elliptic flow study and anti-alpha search.It has also been used to monitor the fraction of clean collisions overbackground collisions during RHIC’s Beam Energy Scan program. Wewill present the architecture, methods and performance of theSTAR HLT. Future developments on accelerating the onlinereconstruction of exotic decay topologies by Graphic Processing Unitwill also be presented.

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Relativistic fluid dynamics from the Boltzmann equation: goingbeyond the 14-moment approximationAuthor: Gabriel Denicol1

Co-authors: Dirk Rischke 2; Etele Molnar 3; Harri Niemi 4

1 Institut fur Theoretische Physik, Goethe University, 60438 Frankfurt am Main, GermanyFrankfurt University2 Institut furTheoretische Physik, Goethe University, and Frankfurt Institute for Advanced Studies (FIAS), 60438 Frank-

furt am Main, Germany3 MTA-KFKI, Research Institute of Particle and Nuclear Physics, H-1525 Budapest, P.O.Box 49, Hungary4 Frankfurt Institute for Advanced Studies (FIAS)


We present a general derivation of relativistic fluid dynamics from the Boltzmann equation usingthe method of moments. In the 14-moment approximation [1,2], traditionally employed in the fluid-dynamical modeling of heavy-ion collisions, fluid dynamics is obtained by explicitly truncating themoment expansion of the single-particle distribution function. In contrast, in our approach all termsof the moment expansion are included and the exact equations of motion for these moments arederived. These exact equations still contain the degrees of freedom and microscopic time scales ofthe Boltzmann equation.

We prove that in order to derive causal fluid-dynamical equations it is necessary to resolve at least theslowest microscopic time scales of the Boltzmann equation, in agreement with [3]. The truncation ofthe equations of motion in terms of only 14 dynamical variables is then implemented by a systematicpower-counting scheme in Knudsen and Reynolds numbers, instead of the explicit truncation of themoment series, as in Israel-Stewart theory. The resulting fluid-dynamical equations and coefficientsare different from the onesobtained via the 14-moment approximation and are in much better agreement with kinetic theory.This means that the fluid-dynamical description of heavy-ion collisions based on the 14-momentapproximation is incomplete.

[1] W. Israel and J. M. Stewart, Phys. Lett. 58 A, 213(1976); Ann. Phys. (N.Y.) 118, 341 (1979).

[2] G. S. Denicol, T. Koide, and D. H. Rischke, Phys. Rev.Lett. 105, 162501 (2010).

[3] G. S. Denicol, J. Noronha, H. Niemi, and D. H. Rischke,accepted for publication in Phys. Rev. D; G. S. Denicol, H. Niemi,J. Noronha, D. H. Rischke, [arXiv:1103.2476 [hep-th]].


Determination of relaxation times at weak and strong coupling

Authors: Dirk Rischke1; Gabriel Denicol2

Co-authors: Harri Niemi 3; Jorge Noronha 4

1 Institut furTheoretische Physik, Goethe University, and Frankfurt Institute for Advanced Studies (FIAS), 60438 Frank-furt am Main, Germany

2 Institut fur Theoretische Physik, Goethe University, 60438 Frankfurt am Main, Germany3 Frankfurt Institute for Advanced Studies (FIAS), 60438 Frankfurt am Main, Germany4 Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, SP, Brazil

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Using linear response theory, we derive [1] conditions for the retarded Green’s function so thatthe linearized equation of motion of a dissipative current is reduced to a relaxation-type equationof the Israel-Stewart type [2]. We prove that this reduction can be done, if the singularity of theretarded Green’s function closest to the origin is a simple pole on the imaginary axis. The relaxationtime coefficient is then given by the location of this pole in the complex plane. This implies thatprevious attempts to derive the relaxation time from the generic long-wavelength, low-frequency(i.e., fluid-dynamical) limit of the retarded Green’s function, via an expansion in terms of gradientsof the fluid-dynamical variables, in general fail to give the correct result.

For a dilute gas, this prescription gives a value for the shear relaxation time that, under certainsimplifying assumptions, coincides with the one derived by matching relativistic fluid dynamics tokinetic theory [3]. This shows that transient fluid dynamics is determined by the slowest microscopicand not by the fastest fluid-dynamical time scale. This has important implications for the descriptionof the collective motion of matter formed in ultrarelativistic heavy-ion collisions, where microscopictime scales and the lifetime of the system itself can be of the same order. We also prove that thelong-wavelength dynamics of the shear stress tensor in a strongly coupled N=4 SYM plasma is notdescribed by relaxation-type equations as in Israel-Stewart theory [2].

[1] G. S. Denicol, J. Noronha, H. Niemi, and D. H. Rischke,accepted for publication in Phys. Rev. D; G. S. Denicol, H. Niemi,J. Noronha, D. H. Rischke, [arXiv:1103.2476 [hep-th]].

[2] W. Israel and J. M. Stewart, Phys. Lett. 58 A, 213(1976); Ann. Phys. (N.Y.) 118, 341 (1979).

[3] G. S. Denicol, T. Koide, and D. H. Rischke, Phys. Rev.Lett. 105, 162501 (2010).


Dielectron Continuum Production from √sNN = 200 GeV pp and

Au+Au collisions at STARAuthor: Jie Zhao1

1 SINAP/LBNL


Dilepton distributions have been proposed as one of the penetrating probes for hot and dense nuclearmatter created in high-energy nuclear collisions. Due to their relatively small final-state interactioncross-sections with the hot/dense environment, dileptons bring us direct information of the createdmatter in such collision. Since dileptons are created over all stages of heavy ion reactions, theirsources vary as a function of kinematics. In the low mass region (LMR: mass<1.1GeV/c2), dilep-tons are dominated by vector mesons and directed photons, while in the intermediate mass region(IMR: 1.1< mass< 3GeV/c2) dileptons are dominated by thermal radiation of quark gluon plasma(QGP). In the high mass region (HMR: mass> 3 GeV/c2), dileptons are mostly contributed by heavy(charm and bottom) quark decays and Drell-Yan processes. As a result, the dilepton distributions,especially in the IMR and HMR, could provide new aspects of early collision dynamics in heavy ioncollisions.

With the completion of the full barrel time-of-flight detector, the electron identification has beensignificantly improved at STAR, especially in low momentum region. In this talk we will presentthe first STAR results on dielectron production in p+p and Au+Au collisions at √sNN = 200 GeV.The results will be compared to hadron decay cocktails to search for vector meson in-medium mod-ifications in LMR and the QGP thermal radiation in IMR. A systematic analysis of the transversemass distributions in IMR region as a function of the mass in Au+Au collisions will be discussed.

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The results will be compared to those from 200 GeV p+p collisions as well as the results from SPSenergies.

Hadron thermodynamics and chemistry / 278

Observation of the antimatter helium-4 nucleus

Author: Liang Xue1

1 SINAP/BNL


We present the observation of the antimatter 4He nucleus, the heaviest observed antinucleus. Theidentification and measurement of anti-4He relies on the mean energy loss per unit track length, thetime of flight of particles, and their curvature in the magnetic field of the STAR detector. Anotheressential detector capability was the High Level online tracking Trigger (HLT), which helps to copewith the large data volume and greatly speeds up the search effort.In total, 18 anti-4He counts were detected at the STAR experiment at RHIC in 109 recorded Au+Aucollisions at beam energies of√sNN = 200 GeV and 62 GeV.Misidentification probability is estimatedto be below 10−11.The invariant differential cross section is consistent with expectations from thermodynamic andcoalescent nucleosynthesis models, which has implications for future production of even heavierantimatter nuclei, as well as for experimental searches for new phenomena in the cosmos. Theyield of the stable antinucleus next in line (mass number = 6) is predicted to be down by a factor of2.6X106 compared to anti-4He and is beyond the reach of current accelerator technology.

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Commissioning and detector performance of the VTX-Pixel de-tector for RHIC-PHENIX experiment.

Author: Ryohji Akimoto1

1 University of Tokyo


Heavy quarks (charm and bottom) is one of the key probes to study properties ofQuarkGluon Plasma(QGP). A silicon vertex tracker (VTX) has been developed for RHIC-PHENIX experiment mainly forthe measurement of the heavy quarks. It enables to measure tracks of charged particles preciselyenough to evaluate yields of charm and bottom individually and therefore is an essential tool tostudy the behavior of charm and bottom inside QGP. It also can be a powerful tool for measurementof long-lived particles, such as hyperon.The VTX is a barrel detector with four layers. It consists of two silicon detectors with differentreadout system, inner two layers are with pixel readout and outer two layers are with strip readout.The VTX was successfully installed at the end of 2010 and started to take physics data. In this posterpresentation, the detector performance of the pixel detector during commissioning and physics datataking is shown.

Heavy flavor / 280

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STAR measurements of bottom to charm ratio and heavy quarkinteractionwith theQCDmedium throughnon-photonic electron-hadron correlationsAuthor: wenqin xu1

1 University of California Los Angeles


FOR THE STAR COLLABORATIONHeavy Quarks are mostly produced through gluon fusions during the initial stage of the heavy ioncollisions. Experimentally heavy quarks are found to suffer a considerable energy loss in the QCDmedium with the nuclear modification factor for non-photonic electrons (NPE) from heavy quarkdecays much smaller than unity in central Au+Au collisions at RHIC. To better understand the heavyflavor production and energy loss mechanism it is crucial to determine experimentally the relativecontributions of Charm and Bottom meson decays to NPE and to study detailed characteristics ofheavy quark interactions with the bulk QCD medium.Wewill present the STARmeasurements of relative charm and bottom contributions toNPE fromp+pcollisions at 200 and 500 GeV energies. We report the total bottom quark production cross sectionfrom p+p collisions at 200 GeV extracted from NPE spectrum and B to D ratios. We will also presentthe NPE-hadron correlations from Au+Au collisions at 200 GeV from the 2010 RHIC run where wehave collected high statistics data set with low photonic conversion background. The evolution of theNPE-hadron azimuthal angular correlation as a function of collision centralities and in comparisonwith that from d+Au collisions will be indicative of dynamics of heavy quark interactions with theQCD medium created in Au+Au collisions. Comparisons with theoretical calculations will also bediscussed.

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Inclusive charged hadron elliptic flow in Au + Au collisions at√sNN = 7.7, 11.5 and 39 GeV

Author: Shusu Shi1

1 the STAR collaboration

We present a systematic study of the transverse momentum (pT ), rapidity and centrality dependenceof elliptic flow, v2, using several methods in Au + Au collisions at √sNN = 7.7, 11.5 and 39 GeV. Thedifference between v2 using event plane from detectors separated in rapidity (v22) and four particlecumulants (v24) seems to decrease as the beam energy decreases. The implications of this resulttowards understanding the energy dependence of non-flow and flow fluctuations will be discussed.The energy dependence of v2 will be presented by a comparison with results from high energies atRHIC (√sNN = 62.4 and 200 GeV), at LHC (√sNN = 2.76 TeV) and similar energy at SPS (√sNN

= 7.6 GeV). We observe the v2(pT ) are very comparable (~10\%) at mid-rapidity and pT > 0.5 GeV/cbeyond √

sNN = 39 GeV. We will also compare our results to transport model calculations, suchas those from UrQMD model, AMPT default model and AMPT string-melting model with differentparton cross sections.


Probing the gluonic structure of matter at a future Electron-IonColliderAuthor: Thomas Ullrich1

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The probing of nuclei and nucleons via deep-inelastic and diffractive processes in the high-energy(low-x) regime will open a new precision window for the investigation of the gluonic structure ofmatter.

Studies of e+p collisions at HERA and especially d+Au collisions at RHIC have found tantalizinghints of saturated gluon densities, a phenomenon with substantial impact on the physics of heavy-ion collisions. Unveiling the collective behavior of densely packed gluons under conditions wheretheir self-interactions dominate will require an Electron-Ion Collider (EIC): a new facility with capa-bilities well beyond those of any existing accelerator. Such a collider could be sited either at BNL orJLAB.

In my talk I will outline the compelling physics case for e+A collisions with a focus on the oppor-tunities for small-x physics. I will discuss the related key measurements and give a brief status ofmachine concepts, detector design, and timeline.

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Directedflowof IdentifiedParticles inAu+AuCollisions at√sNN=39, 11.5 and 7.7 GeV from the STAR ExperimentAuthor: Yadav Pandit1

1 For the STAR Collaboration


Measurements of anisotropic flow in heavy-ion collisionsprovide insight into the early stage of the system’sevolution. Directed flow, v1, is imparted especiallyearly. A change of sign in the slope of dv1/dy foridentified particles, particularly for protons, has beensuggested as a possible signal of a first-order phasetransition. In this talk, we present the STAR measurementsof v1 for π±,K±, protons and antiprotons, aswell as for all detected charged particles in Au + Aucollisions at √sNN = 39, 11.5 and 7.7 GeV as afunction of transverse momentum, rapidity and centrality. At√sNN = 39 GeV, all measured v1 values follow

the trend observed at higher RHIC energies. At√sNN = 11.5 and 7.7 GeV, the proton dv1/dy near

midrapidity changes sign between peripheral and centralcollisions. This behavior is not observed forantiprotons, π± andK±. Results are compared toavailable model predictions.

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Charge-to-Neutral fluctuation in AuAu collisions at Forward ra-pidity at RHIC.Author: Prithwish (for the STAR collaboration) Tribedy1


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Event-by-event fluctuation of the ratio of multiplicities ofcharged and neutral particles at forward rapidity in AuAu collisions at \sqrts_NN=200 GeV hasbeen studied. As the detected charged andneutral particles are mostly from the charged pions and the decay ofneutral pions respectively, this analysis addresses isospin fluctuation of pions predicted to occur fora system going through the QCD chiral phase transition [1][2]. Our study in the STAR experimentat top RHIC energy includes multiplicity measurements of charged particles and photons using theForward Time Projection chamber (FTPC) and the Photon Multiplicity Detector (PMD) respectively.We have used νdyn;ch,γ and rm,1 as measures of dynamical fluctuation & studied their centralitydependence for data & mixed events and compared with the results from HIJNG & UrQMD. A com-parison with results for AuAu collisions at\sqrts_NN=39 GeV will also be discussed to address the energy dependence of charged-to-neutralfluctuation.

Ref:-[1] J.D. Bjorken, What lies ahead?, SLAC-PUB-5673, 1991.[2] J.P. Blaizot, A. Krzywicki, Phys. Rev. D 46 (1992) 246.


Viscous hydrodynamic evolution with non-boost invariant flowfor the color glass condensateAuthor: Akihiko Monnai1

Co-author: Tetsufumi Hirano 1

1 The University of Tokyo


The heavy ion program at LHC opened up a new era in the physics of the quark-gluon plasma (QGP)at higher energies. One of the most unique properties of the hot matter is the near-perfect fluidity,which was first discovered in Au-Au collisions at RHIC [1]. Relativistic hydrodynamic analyses onthe momentum anisotropy of transverse collective flow revealed that small viscosity in the QGPis essential when the initial conditions are constructed from the color glass condensate (CGC), thedescription of saturated gluons in the nuclei before collisions. On the other hand, the dynamicsof the longitudinal flow has scarcely been discussed so far due to the numerical difficulties of thenon-boost invariant viscous hydrodynamic analyses in relativistic coordinates. Since the CGC itselfis considered to be successful in reproducing the observed rapidity distributions and multiplicitiesat RHIC, it would be indispensable to investigate the longitudinal hydrodynamic evolution for theCGC.

We develop a viscous hydrodynamic model with both shear and bulk viscosity and solve the fullsecond-order constitutive equations [2] in the longitudinal direction with the relativistic coordinatesusing a novel numerical approach. The estimations are performed with the CGC-type initial distri-butions for both RHIC and LHC settings. The results exhibit visible and non-trivial deformationsof the CGC rapidity distributions during the hydrodynamic stage due to the interplay between twofactors: (i) Entropy production from non-equilibrium processes and (ii) entropy flux to the forwardrapidity caused by non-boost invariance [3]. We find difference in the hydrodynamic effects at RHICand LHC, which implies that readjustment of the CGC parameters might be necessary. This wouldbe one of the possible explanations for the fact that the CGC predictions tend to underestimate themultiplicity at mid-rapidity observed in the Pb-Pb collisions at LHC experiments [4]. The resultsindicate that non-boost invariant hydrodynamic evolution together with viscosity is indispensablefor understanding the physics of relativistic heavy ion collisions as a whole. We also obtain severalimportant numerical insights towards a full (3+1)-dimensional viscous hydrodynamic model for themore quantitative analyses.

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References:[1] http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=05-38[2] A. Monnai and T. Hirano, Nucl. Phys A 847, 283 (2010)[3] A. Monnai and T. Hirano, arXiv:1102.5053 [nucl-th][4] K. Aamodt et al. [The ALICE Collaboration], Phys. Rev. Lett. 105, 252301 (2010)

Correlations and fluctuations / 287

Hydrokinetic predictions for femtoscopy scales in A+A collisionsin the light of recent ALICE LHC resultsAuthor: Yuriy Sinyukov1

Co-author: Iurii Karpenko 2

1 Bogolyubov Institute for Theoretical Physics2 BITP


A study of energy behavior of the pion spectra and interferometry radii is carried out for the SPS,RHIC and LHC energies within the hydrokinetic approach. The main mechanisms that lead to theparadoxical, at first sight, dependence of the femtoscopy scales on a collision energy, in particular, adecrease of Rout/Rside ratio with the energy growth, are exposed. The hydrokinetic predictions forthe HBT radii at the LHC energies are compared with the recent results of the ALICE experiment.The role of non-equilibrium stage of the matter evolution in the formation of femtoscopy scales atthe LHC energies is analyzed.The results are based on:1. Iu.A. Karpenkov, Yu.M. Sinyukov. Energy dependence of pion interferometry scales in ultra-relativistic heavy ion collisions. Phys. Lett. B 688 50 (2010).2. Yu.M. Sinyukov, Iu.A. Karpenkov. Hydrokinetic predictions for femtoscopy scales in A+A colli-sions in the light of recent ALICE LHC results. arXiv:1103.5632v1 [nucl-th] 29 Mar 2011.3. Very new results based on the Hybrid Hydrokinetic Model (not published yet).

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Mach Cones and Two-Particle Correlations: The Origins in a Ki-netic Transport ApproachAuthor: Ioannis Bouras1

Co-authors: Andrej El 1; Carsten Greiner 1; Felix Reining 1; Francesco Lauciello 1; Harri Niemi 2; Oliver Fochler 1;Zhe Xu 2

1 University of Frankfurt2 FIAS Frankfurt


In a microscopic transport model we investigate evolutionof conical structures using different source terms. Developmentof a strong collective behavior near the ideal hydro limit is visible,resulting in formation of Mach Cones. In addition, for the first timethe transition from ideal to viscous Mach Cones is demonstrated.We investigate dependence of the Mach Cone angle in different scenariosof energy depositions into the medium. The numerical results ontwo-particle correlations are compared to an analytical approximation.

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In our simulations we find that a double-peak structure, as observedin experiments at RHIC, cannot be explained/created by propagation ofa high-energy jet.

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Shear Viscosity of the QGP inCentral A-ACollisions at RHIC andLHC Energies in the Color String Percolation ApproachAuthor: Brijesh Kumar Srivastava1

1 Department of Physics-Purdue University-Unknown


The high-energy heavy ion collisions at RHIC energies have shown evidence of a new state of matterwith very low viscosity to entropy density ratio η/s similar to that of a nearly ideal fluid. The η/sis obtained for the QGP with in the context of the Color String Percolation Model (CSPM) usingdata produced in Au-Au collisions at √sNN = 200 A GeV at RHIC and Pb-Pb at √sNN = 2.76 TeVat LHC [1]. The relativistic kinetic theory relation for η/s is evaluated using CSPM values for thetemperature and the mean free path of the QGP constituents [2].The experimental transverse momentum spectrum is used to measure the percolation density pa-rameter ξ in Au-Au collisions (STAR)[3]. For Pb-Pb at√sNN = 2.76 TeV, ξ values are obtained fromthe extrapolation at RHIC energy. The value of η/s is 0.184 and 0.278 at the CSPM initial temper-ature of 193.6 MeV (RHIC) and 262.2 MeV (LHC), respectively. These values are 2.3 and 3.5 timesthe AdS/CFT conjectured lower bound 1/4π. We compare the CSPM η/s(T/Tc) analytic expressionwith weak coupling (wQGP) and strong coupling (sQGP) calculations. This indicates that the QGPis a strongly coupled fluid in the phase transition region.

[1] M. A. Braun, C. Pajares, Eu. Phys. J. C16, 349 (2000).[2] T. Hirano, M. Gyulassy, Nucl. Phys. A769, 71 (2006).[3] R. P. Scharenberg, B. K. Srivastava and A. S. Hirsch, Eur. Phys. J. C71, 1510 (2011).

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Finite lifetime effects on the photon production from a quark-gluon plasmaAuthor: Frank Michler1

Co-authors: Björn Schenke 2; Carsten Greiner 1

1 University of Frankfurt2 Brookhaven National Laboratory


Direct photons play an important role as electromagnetic probes from aquark-gluon plasma (QGP) created in heavy-ion collisions. After beingonce produced, they leave the medium undisturbed an thus provide direct insight into the early stageof the collision. We use the real time Keldysh formalism to investigate how non-equilibrium effectssuch as a finite lifetime modify the resulting photon spectra. We provide an ansatz which eliminatesthe divergent contribution from the vacuumpolarization and renders the photon spectrum UV-finite if the timeevolution of the QGP is described in a suitable manner.

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Elliptic Flow of charged particles in Au+Au collisions at √sNN =7.7, 11.5 and 39 GeV from STARAuthor: Michael K. Mitrovski1

1 for the STAR collaboration


The study of elliptic flow and non-flow effects over a wide energy range can provide informationon the onset of collective effects in heavy-ion collisions. In 2010, STAR collected high statistics datasamples at lower RHIC energies at √sNN = 7.7, 11.5 and 39 GeV. We will present measurements ofcharged particle elliptic flow using the event-plane (v2EP) determined from detectors separatedin eta, 2-particle (v22) and 4-particle (v24) correlation methods integrated over pt and η alongwith differential elliptic flow v2(pt) and v2(η). The difference using v2EP, v22 and v24decreases with decreasing the beam energy. In addition we observe that no large differences (∼10\%)are visible for the pt dependence (| η |< 1.0 and pt > 0.5) of v24 starting from√

sNN = 39 GeV. Achange of the energy dependence is observed in the difference between v222 and v242 which isrelated to v2 fluctuations (σv2 ) and non-flow correlations (δ2). The measurements will be comparedto measurements at SPS, higher RHIC and LHC energies, as well as string hadronic/partonic andhydrodynamic model calculations.

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Low-mass meson production through di-leptonic decays in p+pand Au+Au collisions at √s

NN= 200 GeV from STAR

Author: Bingchu Huang1

1 STAR BNL


Ultra-relativistic heavy ion collisions provide a unique environment to study the properties of strongly-coupled Quark Gluon Plasma (sQGP) at high temperature and high energy density. One of thecrucial probes to study the sQGP is the di-electron production in the low (Mll < 1.0GeV /c2) andthe intermediate (1.0<M_ll<3 GeV/c^2)massregion.Intheintermediatemassregion, thedi−electronproductionaredirectlyrelatedtothermalradiationofthesQGP.Inthelowmassrange, wecanstudytheproductionofvectormesonsinthemedium,whereanymodificationsobservedmayrelatetothepossibilityofchiralsymmetryrestoration.ThenewlyinstalledSTARBarrelT ime−of−Flightdetector(TOF )provideshighacceptanceandefficiencyforchargedparticleidentificationatmid−rapidity.Bycombiningthetime−of−flightfromtheTOFandtheenergylossfromTimeProjectionChamber, STARisabletoidentifyelectronwithhighpurityfromlowtointermediatetransversemomentumatmid−rapidity.Inthistalk, wepresentthemeasurementsofvectormeson\omegainvariantyieldsviadi−electrondecaysin200GeV p+pandAu+Aucollisionsandthedi−electroncontinuumspectrumin200GeV p+pcollisionsatmid−rapidity.Theperspectiveonpossiblecomparisonsbetween\rho\righarrow e^+e^-and\rho\righarrow pi^+ pi^-andlimitson\eta\rightarrow e+e-$ will be discussed.


Chirality, magnetic field and parity violation in hot QCD mat-terAuthor: Dmitri Kharzeev1

1 Stony Brook and BNL

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An overview of the recent progress in understanding the interplay ofquantum anomalies, chirality, and magnetic field in the dynamicsof QCD fluid will be presented. The current theoretical descriptionof the chiral magnetic and chiral vortical effects within anomalousmagnetohydrodynamics will be described. It allows a quantitativeapproach to these phenomena in heavy ion collisions, andthe first results from such studies will be reviewed.The existing and future experimental measurements needed toestablish or refute the local violation of parity in hot QCD matterwill be discussed.

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Leptonic decay of phi(1020) meson measured with the STAR ex-perimentAuthor: Christina Markert1

1 University of Texas at Austin


Hadronic resonances can play a pivotal role in providing experimentalevidence for partial chiral symmetry restoration in the deconfinedquark-gluon phase produced at RHIC and the LHC. Their lifetimes, whichare comparable to the lifetime of the fireball, make thema valuable tool to study medium modifications to the resonant statedue to the chiral phase transition signatures of mass shifts and/or width broadenings. This can bedone via the leptonic decay of resonances, however hadronic regeneration of resonances feeds intothis signature as well.We will present the measurement of phi(1020) at mid-rapidity in p+p collisionsand the preliminary results of the resonance signal in Au+Au collisions at 200 GeV using the STARupgrade Time of Flight detector for electron identification.

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Finite-size scaling search for the critical endpoint ofQCD inheavyion dataAuthor: Eduardo Fraga1

Co-authors: Leticia Palhares 2; Paul Sorensen 3

1 Universidade Federal do Rio de Janeiro2 Institut de Physique Theorique, CEA/Saclay3 Brookhaven National Laboratory


Given the short lifetime and the reduced volume of the quark-gluon plasma (QGP) formed in high-energy heavy ion collisions, a possible critical endpoint (CEP) will be blurred over a region and theeffects from criticality severely smoothened. Nevertheless, the non-monotonic behavior of correla-tion functions near criticality for systems of different sizes, given by different centralities in heavyion collisions, must obey finite-size scaling. We apply the predicting power of scaling plots to thesearch for the CEP of strong interactions in heavy ion collisions using data from RHIC and SPS.

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The results of our data analysis suggest that a critical point cannot be below chemical potentialsµ ∼ 450 MeV. Extrapolating the analysis, we speculate that criticality could appear slightly aboveµ ∼ 500MeV. Using available data we extrapolate our scaling curves to predict the behavior of newdata at lower center-of-mass energy, currently being investigated in the Beam Energy Scan programat RHIC.

Energy scan / 297

Identified hadron production from the RHIC beam energy scanprogram in the STAR experimentAuthor: lokesh kumar1

1 Kent State University


A current focus at RHIC is the Beam Energy Scan (BES) program to study the QCD phase diagram —temperature (T ) vs. baryon chemical potential (µB). The BES program aims to verify some predic-tions fromQCD: that a cross-over occurs at µB = 0, and that there exists a first-order phase transitionat large µB and a critical point at an intermediate µB . The spectra and ratios of produced particlescan be used to extract T and µB in different energies and system sizes.

The Solenoidal Tracker At RHIC (STAR) experiment has collected data for Au+Au collisions at√sNN = 7.7 GeV, 11.5 GeV, and 39 GeV in year 2010. One of the advantages during the BES pro-

gram was the enhanced particle identification with availability of full Time-Of-Flight detector. Inaddition, STAR collected Cu+Cu collisions at22.4 GeV in year 2005. We present mid-rapidity spectra (pT ormT −m0), rapidity density, averagetransverse mass, and particleratios for identified hadrons from the STAR experiment. The centrality and transverse momentumdependence of the particle yields and ratios will be compared to existing data at lower and higherbeam energies and to various transport models like AMPT and UrQMD. Collision dynamics are stud-ied systematically in the framework of chemical and kinetic freeze-out and their properties extractedfrom the particle ratios and spectra.

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Multiparticle system in high energy hadronic/nuclear collisionand matter state of early universeAuthors: R. Klippert1; Shi-Yuan Li2; V. A. De Lorenci1

1 UNIFEI2 SDU


The universe is expanding, hence in early times it was more dense than it is today. The spacetimecurvature becomes arbitrarily large around the singular point, leaving room for arbitrarily large en-ergetic processes as well as arbitrarily dense matter states to take place. The matter states of thelargest densities that human being can produce and study microscopically in laboratory arethose generated in high energy collisions. Thematter state appearing just after the inelastic hadronic/nuclearcollisions is taken as the dominant matter-energy content ofthe universe. Working on the central rapidity plateau, anonsingular and anisotropic toy-model presenting aninflationary phase that naturally evolves to a decelerated expansioncan be obtained. Moreover, by considering the specific state of the glasma fluid at small time scales,

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an solution describing the evolution of the spacetime is presented.These simple examples of the collider physics motivated cosmology show that the multiparticle sys-tem produced in collision can shed light on the matter state of early universe.

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Viscous relaxation time in relativistic hydrodynamicsAuthor: Xu-Guang Huang1

Co-author: Dirk Rischke 1

1 Institute for Theoretical Physics


Relativistic Navier-Stokes hydrodynamics is acausal and unstable. These problems are solved byintroducing relaxation times into the constitutive equations of the viscous tensors. We derive themicroscopic formulae of the shear and bulk viscous relaxation times by using the projection oper-ator method. In the leading-order of perturbative calculation, we find the ratios of the viscositiesand corresponding relaxations times are purely thermodynamic functions and independent of thescattering details.

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Energy dependence of the freeze out eccentricity from azimuthaldependence of HBT at STARAuthor: Christopher Anson1



Non-central heavy ion collisions at RHIC create an anisotropic participant zone of QCDmatter underextreme conditions of energy and matter density. While this zone is initially out-of-plane-extended,pressure gradients cause the hot, dense medium to expand preferentially in plane. Over time, thisexpansion makes the shape more spherical, perhaps even becoming extended in the in-plane direc-tion. The change in shape is determined by the expansion and freeze-out time scales which depend,in part, on the early pressure gradients. As a result, the freeze-out shape may provide a sensitiveprobe of the Equation of State of hot QCD matter.

The recent RHIC Beam Energy Scan at \protect $\sqrts_NN$ of 7.7, 11.5, and 39 GeV provides an opportunity to explore the energy dependence of the freeze out eccentricity. The new low energy data from STAR complements high statistics data sets at \protect $\sqrts_NN$ of 62.4 and 200 GeV. The dependence of the HBT radius parameters on azimuthal angle relative to the reaction plane have been extracted. These dependences can be related to the freeze out eccentricity within the context of a blast wave model. We will present STAR's most recent results on azimuthally-dependent HBT across a wide range of energies.

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D0meson production in pp collisions at the LHCwith ALICE andprospects for charm flow measurements in PbPb collisionsAuthor: Chiara Bianchin1

1 Universita degli Studi di Padova-Universita & INFN, Padova-Unkn

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The ALICE experiment at LHC studies p-p and Pb-Pb collisions with the aim of investigating theproperties of the high-density state of strongly-interacting matter, expected to be produced in Pb-Pbcollisions.D mesons are powerful probes of the medium since the charm quark is produced in a very shorttime scale and experiences all the evolution of the collision.The measurement of the azimuthal anisotropy of D mesons production in PbPb semi-peripheralcollisions is one of the goals of the heavy flavour physics program because directly related to theheavy quark elliptic flow.The measurement of open charm production in p-p collisions, besides providing a reference for thestudy of nuclear effects in Pb-Pb collisions, is very interesting per se, as a test of perturbative QCDpredictions at the high energy frontier.The ALICE detector is well suited to accomplish these measurements thanks to the precise vertexreconstruction, tracking and PID capabilities.In this poster the preliminary results on the D^0 production cross section in pp collisions, obtainedby the D^0->Kpi channel, will be presented and the prospects for the measurement of the ellipticflow will be described.

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Phenomenological interpolation of inclusive J/psi production toproton-proton collisions at sqrt(s)=2.76 TeV and 5.5 TeVAuthors: Alessandro De Falco1; Francesco Bossù2; Ginés Martínez García3; Martino Gagliardi4; Smbat Grigoryan5;Zaida Conesa del Valle6

1 Università and Sezione INFN di Cagliari, Cagliari, Italy2 Università degli Studi and Sezione INFN di Torino, Torino, Italy3 Subatech, Ecole des Mines de Nantes, Université de Nantes, CNRS-IN2P3, Nantes, France4 Sezione INFN di Torino, Torino, Italy5 JINR, Dubna, Russia and YerPhI, Yerevan, Armenia6 European organization for Nuclear Research (CERN), Genève, Switzerland


J/psi production is one of the key measurements in heavy-ion collisions at the LHC. It is expected toprovide means to discriminate between different scenarii, ranging from full suppression by colourscreening to enhancement by charm quark pair recombination.

In 2010, the LHC delivered Pb-Pb collisions at the center of mass energy per nucleon pair of 2.76 TeV.The knowledge of the J/psi cross section in p-p collisions at the same energy is crucial for a correctinterpretation of the data.

We perform an interpolation of the inclusive J/psi cross section to p-p collisions at sqrt(s)=2.76 TeV(and sqrt(s)=5.5 TeV), based on the available experimental data.First, we describe the energy dependence of the J/psi cross section at mid-rapidity. Second, we studythe rapidity dependence of J/psi production and provide estimates for the cross section in the forwardrapidity regions of interest for the LHC experiments. Third, we develop the tools to extrapolate thetransverse momentum distributions.In our approach, we adopt both phenomenological and pQCD-driven techniques and, where possible,we combine them.

Our study is documented in arXiv:1103.2394 [nucl-ex]; it is meant to be complementary and providean useful cross-check to the measurements performed during the recent p-p data-taking campaignat sqrt(s)=2.76 TeV at the LHC.

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Direct photons at low transverse momentum – a QGP signal inpp collisions at LHCAuthor: Fuming Liu1

Co-author: Klaus Werner 2

1 Huazhong Normal University2 Subatech


We predict that direct photon production in pp collisions at 7~TeVwill get at least 10 times enhanced compared to the next to leadingorder pQCD predictions, at low transverse momentum (ptlesssim10~GeV/c), due to the thermal photon emissions from a quark gluon plasma(QGP) formed in high multiplicity events. Thus the enhancement ofdirect photon production at lowpt can be a QGP signal in pp collisions.


Exploring compressed nuclear matter with HADESAuthor: Piotr Salabura1

1 IFUJ


In the energy domain of 1-2 GeV kinetic energy per nucleon, HADES has been performed systematicstudies of electron-positron production in C+C, Ar+KCl, p+p, d+p and p+Nb collisions. Our resultsdemonstrate that electron pair emission in small collision systems, such as C+C, can essentially beexplained as a superposition of independent N+N collisions with a dominant contribution from thep-n channel.

The comparison of the N+N reference spectrum with the di-electron invariant-mass distributionmeasured in Ar+KC collisions shows a pronounced excess radiation. The properties of the excess asa function of the transverse mass are quantified.

Further medium effects have been investigated in p+Nb interactions at 3.5 GeV by a direct compari-son to p+p reactions measured at the same energy. Differential dielectron production cross sectionshave been extracted and can be compared in detail in the pi^0, eta and the vector meson regions.The results will be discussed and compared to the ones obtained in photo-induced reactions.

Intriguing results were also obtained from the reconstruction of hadrons with open and hiddenstrangeness in Ar+KCl collisions. While the measured abundance of all reconstructed particles arewell described assuming thermalization, the also reconstructed double-strange baryon Xi^- appearsabout ten times more abundant than expected. Also, the phi/omega ratio is much larger than theone measured in N-N collisions and does not require any OZI suppression.

Further investigations of compressed nuclear matter by means of di-electrons as penetrating probesand strangeness productionwill be followed up over the forthcoming yearswith an upgradedHADESdetector in Au+Au and Ag+Ag collisions.

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Dynamics near QCD critical point by dynamic renormalizationgroupAuthor: Yuki Minami1

1 Japan


We study the critical dynamics near QCD critical point (CP)by dynamic renormalization group (RG).As a basic equation for the critical dynamics,we construct the nonlinear Langevin equation,which is a standard dynamic equation for a CP in condensed matter physics.Our onstruction is based on the generalized Langevin equetion and the relativistic hydrodynamics.Applying the dynamic RG to the constructed equation,we derive the RG equation for the transport coefficientsand obtain their critical exponents.We find that the resulting RG equation turns out to be the same as that for the liquid-gas CP,alhough the Langevin equations for the two critical points are different.Therefore, the bulk viscosity and the thermal conductivity strongly diverge at the QCD CP.We also show that the thermal and viscous diffusion modes exhibit critical slowing down.In contrast, the sound mode shows critical speeding up.

Reference

Y.Minami arXiv:1102.5485 [hep-ph]

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QCD Phase Diagram based on Strong Coupling Lattice QCDAuthor: Takashi Nakano1

Co-authors: Akira Ohnishi 2; Kohtaroh Miura 3

1 Kyoto University2 Yukawa Institute for Theoretical Physics3 INFN-Laboratori Nazionali di Frascati


In RHIC and FAIR experiments, it is important to search the position of the critical point and first-order phase boundary in QCD phase diagram.Strong Coupling Lattice QCD has been applied to investigate the chiralphase transition at finite temperature and chemical potential. We takeaccount of thechiral and deconfinementphase transitions in the strong coupling lattice QCD, and investigatethe QCD phase diagram. In this study, the calculated criticaltemperature at zero chemical potential almost reproduces the resultsof Monte Carlo simulations in the strong coupling region. Bycomparison, in the finite chemical potential region, Polyakov loopeffectsreducethe critical point temperature and the first order chiral phasetransition line shrinks.

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Sensitivity of the elliptic flowcoefficient to a temperature-dependentshear viscosity-to-entropy density ratio in ultrarelativistic heavy-ion collisions at RHIC and LHCAuthor: Harri Niemi1

Co-authors: Dirk Rischke 2; Etele Molnár 3; Gabriel Denicol 4; Pasi Huovinen 4

1 Frankfurt Institute for Advanced Studies2 Frankfurt Institute for Advanced Studies; Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität3 Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität; MTA-KFKI, Research Institute of Particle

and Nuclear Physics4 Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität


We investigate the effects of a temperature-dependent shearviscosity-to-entropy density ratio η/s on the ellipticflow of hadrons in ultrarelativistic heavy-ion collisions [1].We use relativistic dissipative fluid dynamics to model thespace-time evolution of the hot and dense system formed insuch collisions. The final hadron spectra are calculated usingthe Cooper-Frye freeze-out procedure.

By studying different parametrizations for the temperaturedependence of η/s, we found that the viscous suppressionof the elliptic flow coefficient in √

sNN = 200 GeVAu+Au collisions at the Relativistic Heavy Ion Collider (RHIC)is dominated by the viscosity in the hadronic phase and in thephase transition region. However, the elliptic flow at RHIC islargely insensitive to the viscosity of thequark-gluon plasma (QGP).

On the other hand, we found that sensitivity of the ellipticflow to the high-temperature η/s increases with increasingmultiplicity and simultaneously the sensitivity to the hadronicviscosity decreases. At the highest LHC energy, the ellipticflow becomes sensitive to the QGP viscosity and insensitive tothe hadronic viscosity.

The change of the sensitivity from hadronic to QGP viscosityfrom RHIC to LHC can provide access to determining thetemperature dependence of η/s from elliptic flow data.

[1] H. Niemi, G. S. Denicol, P. Huovinen, E. Molnar, D. H. Rischke,[arXiv:1101.2442 [nucl-th]].

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Chiral transition in a magnetic field and at finite baryon den-sityAuthor: Jens O.Andersen1

Co-author: Rashid Khan 1

1 Norwegian University of Science and Technology

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We study the quark-meson model with two quark flavors in a strong external magnetic field atfinite temperature and finite baryon chemical potential.We calculate the full renormalized effectivepotential to one loop order in perturbation theory.While the critical temperature in the chiral limitis almost unchanged and compared to the case with zero external magnetic field, the transition isbecoming more strongly first order.

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Suppression of large transverse momentum hadrons in centralPb+Pb collision at LHCAuthor: Subrata Pal1

1 Tata Institute of Fundamental Research, Mumbai, India


Quenching of high transverse momentum hadrons formed in Pb+Pb collisions at the center-of-massenergy of 2.76 TeV is studied within A MultiPhase Transport (AMPT) model. The initial conditionsfor quark and gluon jet production are obtained from the recently updated HIJING 2.0 model thatinvokes the latest parton distribution function as well as an energy dependent cut off momentumparameter p_0 for jet production in the two-component model. Once the parameters of the modelhas been fixed by reproducing the measured charged particle spectra in p+p collisions at the LHCenergy regime, we shall demonstrate that the centrality dependence of charged particle multiplic-ity in Pb+Pb collisions is mostly controlled by the gluon shadowing at small transverse momentum.We shall show within the AMPT model that simultaneous reproduction of the measured centralitydependence of charged hadrons and the quenching of high transverse momentum hadrons, quanti-fied by the nuclear modification factor R_AA, could further constrain the parton-parton scatteringcross section to a rather small value at the LHC energy.


Turbulent fluctuations around Bjorken flowAuthor: Stefan Floerchinger1

Co-author: Urs Achim Wiedemann 1

1 CERN


For large Reynolds number (which is inverse to viscosity), fluids are known to develop turbulence.Therefore, the phenomenological evidence for a small viscosity suggests that the hydrodynamicaldescription of heavy ion collisions may have a turbulent regime. Assuming that averaged velocitiesare described by Bjorkens model, we investigate local fluctuations around it. These perturbationsare governed by non-linear equations and we characterize classes of qualitatively different evolutionin terms of Reynolds numbers. Perturbations at different rapidities are found to decouple quickly,and the local evolution becomes effectively two-dimensional. The resulting Navier-Stokes equationof non-relativistic form (obtained after suitable coordinate transformations) can be discussed withinthe theory of Kolmogorov and Kraichnan. In particular, unlike three-dimensional turbulent flow,two-dimensional viscous fluid dynamics can show the interesting phenomenon of inverse cascadingof energy into large scale structures. We speculate on possible phenomenological implications ofthese findings.

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Medium-induced modifications of color flow in high transversemomentum processesAuthors: Andrea Beraudo1; José Guilherme Milhano2; Urs Wiedemann3

1 Centro Studi e ricerche ”Enrico Fermi” - Rome (Italy)2 Advanced Research Fellow and Invited Professor , CENTRA-IST (Lisbon) and Scientific Associate, CERN-PH-TH3 CERN-PH-TH


Heavy ion collisions at both RHIC and the LHC show strong medium-induced modifications of high-pT single inclusive hadron spectra, jet-like particle correlations and reconstructed jets.A dynamical understanding of these jet quenching phenomena is typically sought within a partonicpicture in which the energy of highly energetic parent partons is degraded due tomultiple inelastic and/or elastic interactions inside QCD matter.In the current model implementations of this parton energy loss the hadronization process is unaf-fected by it on account that for sufficiently energetic projectiles time dilation should guarantee theirhadronization outside the medium.However, as it has been pointed out before, the interaction of a colored parton with a QCD mediummodifies the color flow of the parton shower and arguably can imprint on the hadronization processat much higher transverse momentum than estimated previously.In this context, we present here the first QCD-based calculation of medium-induced color flow.Decomposing the multiple scattering diagrams of the BDMPS-Z formalism for parton energy lossinto color-singlet ‘prehadronic’ systems, we observe that (in comparison to vacuum fragmentation)medium-inducedeffects do not only degrade the longitudinal momentum of these color-singlet systems but alsostrongly enhance their invariant mass. The larger the invariant mass of a color-singlet at the end ofthe perturbative evolution, the more likely it is for such system to decay into a larger number ofhadronic fragments and thus leave a smaller fraction of the total available energy to the leadinghadron.Therefore, for multi-partonic states that show the same kinematic distributions at the end of theperturbative evolution, medium-modified color flow can be a significant additional source ofmedium-induced multiplicity increase and medium-induced degradation of the leading hadron.We illustrate this general observation in simple models. We also identify a color flow specific forma-tion time argument that indicates that effects of color-flow induced additional suppressioncan persist over transverse energies up to tens of GeV, and may contribute to an enhanced slope ofthe nuclear modification factor.

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Probing deconfinementwith chiral effectivemodels at imaginarychemical potentialAuthor: Kenji Morita1

Co-authors: Bengt Friman 2; Krzysztof Redlich 3; Vladimir Skokov 2

1 Kyot University2 GSI3 University of Wroclaw


The sign problem in lattice QCD prevents us from directly evaluatingthermodynamics at real quark chemical potential since the Dirac determinanttakes complex value. At imaginary chemical potential, this quantity

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becomes real thus Monte-Carlo simulation is possible.One needs an analytic continuation to relate a quantity obtainedat imaginary chemical potential to a real one. Some characteristicfeatures, however, have been found also at the imaginary chemical potentialas realization of the symmetries possessed by QCD. Therefore, the imaginarychemical potential provides us additional information on the rich phasestructure of QCD.

In this work, we investigate the phase structure of Polyakov loop-extendedchiral effective models at imaginary chemical potential with a particularemphasis on the confinement-deconfinement transition.First we discuss the phase transitions in the PNJL and PQM models for differentimplementations of the Polyakov loop potential, within the mean fieldapproximation. We find a critical endpoint of the deconfinement transitionat imaginary chemical potential, of which origin is shown to nicelyillustrate interplay between the chiral transition and the deconfinement.Second, we discuss how to characterize the deconfinement transition byutilizing the imaginary chemical potential in analogy with the so-calleddual order parameter. Finally, we discuss the effect of the quantumfluctuation on the determination of the phase diagram in the PQM modelby making use of the functional renormalization group approach.

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Charmonium mass in hot and dense hadronic matter from QCDsum rules

Author: Kenji Morita1

Co-author: Su Houng Lee 2

1 Kyot University

2 Yonsei University


Charmonia in medium provide us information on the change of the confinementproperty induced by the medium. We have developed an approach based onQCD sum rule which connects temperature dependent QCD condensates tothe spectral function through the operator product expansion of thecurrent correlation function.The leading contribution to the OPE is the dimension four gluoncondensate which suddenly drops in the vicinity of the deconfinementtransition temperature therefore can be regarded as an effective orderparameter. We showed that this behavior is related to the correspondingchange of the spectral property of the charmonia and is consistent withlattice QCD measurement of the imaginary time correlators.In this work, we further extend our prescription to utilize more realisticgluon condensates measured by lattice QCD with physical quark masses.By making use of the resonance gas model, we determine the gluon condensatesat nonzero baryonic chemical potential and explore the charmonia at temperatureand chemical potential which are accesible with current and futureexperiments. We show that the reduction of the charmonium mass will leadto change of particle ratio in the statistical hadronization scenario.


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Determining initial state fluctuations from flow measurements

Author: Jean-Yves Ollitrault1

Co-authors: Matthew Luzum 2; Rajeev Bhalerao 3

1 SPhT, Saclay2 IPhT Saclay3 TIFR, Mumbai


Long-range azimuthal correlations are generated by fluctuations of theinitial energy distribution, followed by collective flow.We list eight independent observables which can be measured usingmultiparticle azimuthal correlations in the first three Fourierharmonics. Some of these observables are already well known, such asv22 and v24, but most of them are new, in particular,the joint correlations between v1, v2 and v3.We show that by taking ratios of these observables, one can constructquantities which are largely independent of the hydrodynamic response of the medium, and thusare solely determined by initial fluctuations.We present predictions for these ratios using a Monte-CarloGlauber model and a Monte-Carlo KLN model, and compare to existingdata from STAR and ALICE.

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Understanding initial state fluctuationsAuthor: Rajeev Bhalerao1

Co-authors: Jean-Yves Ollitrault 2; Matthew Luzum 2

1 TIFR (Tata Inst. of Fundamental Research)2 IPhT (CEA/Saclay)


In event-by-event hydrodynamics, the initial distribution of participants in the azimuthal plane fluc-tuates from event to event. We study the dipole asymmetry ϵ1, eccentricity ϵ2, and triangularity ϵ3,as a function of centrality, both analytically as well as numerically. These Fourier harmonics of theinitial-state geometry have been shown to largely determine the flow coefficients v1, v2, and v3, re-spectively, in hydrodynamic calculations, and so are of significant theoretical interest. We considerfluctuations in the centre-of-mass of the participant distribution to order 6. In an independent-sourcemodel, we derive expressions for ϵ32, ϵ34, ϵ12, and various correlations among the orienta-tion angles ψ1, ψ3 and ψ2 ≡ ΨPP which is the participant-plane angle. We compare these analyticresults with numerical results based onMonte-Carlo Glauber andMonte-Carlo KLNmodels. We findthat the independent-source model explains many of the features seen in the Monte-Carlo models,and thus can provide insight into the fluctuations seen in heavy-ion collisions.

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Ratio of J/Psi to Rho Photoproduction Cross Sections at the Rel-ativistic Heavy Ion Collider with STARAuthor: Janet Seger1

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1 Creighton University


The intense electromagnetic fields associated with relativistic heavy ions make a heavy-ion collidera unique tool to study two-photon and photonuclear interactions. In this talk, we present a newmeasurement of J/psi photoproduction in 200 GeV AuAu collisions at RHIC. The pT distribution ofthe J/psi mesons peaks at very low pT, consistent with expectations for coherent photoproduction.Both the photoproduction cross section and the J/psi rapidity distribution are expected to show theeffects of gluon shadowing. We present a measurement of the ratio of J/psi to rho^0 meson crosssections in 200 GeV AuAu collisions, as well as a distribution of rapidity within |y| < 1 for the J/psimesons. The measured results are compared to theoretical models.

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Jet-Hadron Correlations in STARAuthor: Alice Ohlson1

1 Yale University


In recent years, the study of dihadron correlations has been one of the primary methods used toinvestigate the propagation and modification of hard-scattered partons in the QGP. Due to recent ad-vancements in jet-finding algorithms it is now possible to use reconstructed jets in these correlationstudies. This increases the kinematic reach of such analyses and improves the signal-to-backgroundratio.

We show results of a systematic study of jet-hadron correlations in 200 GeV central Au+Au colli-sions, which are indicative of a broadening and softening of jets which interact with the medium.Furthermore, jet-hadron correlations suggest that the suppression of the associated hadron yield athigh-pT is balanced by low-pT enhancement.

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Bulk viscosity in heavy-ion collisionAuthor: Kevin Dusling1

1 North Carolina State University


In this work we examine the bulk viscous correction to the distribution function (δf ) in both the re-laxation time approximation and from weakly coupled QCD. We then incorporate this bulk viscouscorrection in 2+1 Dimensional viscous relativistic hydrodynamics and compute particle spectra andelliptic flow. Since the thermal mass for quark and gluons are different the departures from equilib-rium are also different. We explore how a species dependent bulk viscous δf affects particle spectraand how the bulk and shear viscous effects can possibly be separated in the data.


Lattice QCD based equation of state at finite baryon density

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Author: Pasi Huovinen1

1 Johann Wolfgang Goethe-Universität


The effects of non-zero baryon density are expected to become importantin hydrodynamicmodeling of heavy collisions below the highest energy at RHIC. Recent calculationsin effective models and in QCD using Dyson Schwinger equation suggest that the transition in QCDremains a crossover up to baryon chemical potentials of about 800MeV [1]. If so, the equation of staterelevant for hydrodynamic models can be calculated on the lattice using Taylor expansion. However,there are large cutoff effects in present lattice calculations for non-zero chemical potentials.

We employ the latticeQCDdata on Taylor expansion coefficients [2] to extend our previous parametriza-tion of the equation of state [3] to finite baryon density. When we take into account lattice spacingand quark mass dependence of the hadron masses [3], the Taylor coefficients at low temperatureare equal to those of hadron resonance gas. Therefore we require require that the equation of stateis smoothly connected to the hadron resonance gas equation of state at low temperatures. Somepreliminary results were reported in [4].We also show how the hydrodynamical evolution is affected by this equation of state in the energyrange relevant for SPS and the RHIC energy scan.

[1] T.K. Herbst et al, Phys. Lett. B696 (2011);C.S. Fischer et al, arXiv:1104.1564

[2] M. Cheng et al, Phys. Rev. D79 (2009) 074505;C Miao and C. Schmidt,PoS LATTICE2008 (2008) 172

[3] P.Huovinen and P.Petreczky, Nucl.Phys. A837 (2010) 26

[4] P.Huovinen and P.Petreczky, J. Phys. Conf. Ser. 230 (2010) 012012

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D0 production in p+p sqrts = 200 GeV collisions at STARAuthor: David Tlusty1

1 NPI ASCR


The charm production is sensitive to early dynamics of the created systemin RHIC heavy ion collisions. Dominant process of charm quark productionat RHIC is believed to be initial gluon fusion which can be calculated in theperturbative QCD. Understanding both the charm production total crosssection and the fragmentation in p+p collisions is a baseline tofurther explore the QCD medium via open charm and charmonium in heavy ion collisions.

This poster will present the reconstruction of open charm meson D0

via the weak decay to K and π mesons in the p+p collisions at midrapidityfor sqrts = 200 GeV.The analysis is based on the large p+p minimum bias samplecollected in RHIC year 2009 by the STAR detector. The Time-Of-Flight detector,which covered 72% of the whole barrel in year 2009, was firstly used to improvethe decay daughter identification. The open charm cross section from hadronicdecay channel will be presented.

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Transition temperature and the equation of state from latticeQCD,Wuppertal-Budapest resultsAuthor: Zoltan Fodor1

Co-authors: Antal Jakovac 2; Christian Holbling 1; Gergely Endrodi 3; Kalman Szabo 1; Sandor Katz 4; Stefan Krieg1; Szabolcs Borsanyi 1

1 BUW2 Budapest Technical University3 University of Regensburg4 ELTE


The QCD transition is studied on lattices up to Nt=16. The strange susceptibility the chiral conden-sate and the renormalized Polyakov loops are presented. The equation of state is determined onlattice with Nt-6,8,10 and at some temperature values with Nt=12. The pressure, the trace anomaly,the energy and entropy density and the speed of sound are presented as functions of the temperaturein the range 100 …1000 MeV . We give estimates for the pion mass dependence and for the contri-bution of the charm quark. We compare our data to the equation of state obtained by the “hotQCD”collaboration.

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Forward-Backward Multiplicity Correlations for Identified Parti-cles at STARAuthor: Michael Skoby1

1 Purdue University


Long-Range Forward-Backward multiplicity correlations(LRC) may be a signal for multiple partonicinteractions in dense matter, whereas short-range correlations are due to independent sources [1,2].Previously, strong LRC have been measured at STAR in 200 GeV central Au+Au collisions, and wereshown to decrease with decreasing centrality [3]. The Color Glass Condensate model, which de-scribes sources as longitudinal flux tubes, predicts that the correlation will grow with centrality[4,5]. Furthermore, fluctuations in the number of gluons at early times will produce a long rangecorrelation significantly larger for pions than protons [5]. We present the forward-backward corre-lation of identifiedhadrons (pions, kaons, protons) as a function of rapidity for Au+Au collisions at sqrt(s_NN) = 200GeV. The particle identification is carried out by measuring their average energy loss in the STARTime Projection Chamber. The centrality dependence of the correlation strength will also be dis-cussed for each particle species.

References:

[1] A. Capella and A. Krzywicki, Phys. Rev. D 18, 4120 (1978).

[2] A. Capella et al., Phys. Rep. 236, 225 (1994).

[3] B. I. Abelev et al. (STAR Collaboration), Phys. Rev. Lett.103, 172301 (2009).

[4] Y. V. Kovchegov, E. Levin, and L. McLerran, Phys. Rev. C63, 024903 (2001).

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[5] N. Armesto, L. McLerran, and C. Pajares, Nucl. Phys. A 781,201 (2007).


Elliptic and triangular flow in the event-by-event 3+1D viscoushydrodynamicsAuthor: Sangyong Jeon1

Co-authors: Bjoern Schenke 2; Charles Gale 1

1 McGill University2 Brookhaven National Lab


I will present results for elliptic and triangular flow coefficientsv2 and v3 in Au+Au collisions atsqrt(s) = 200A GeV using event-by-event 3+1D viscous hydrodynamic simulations. I will reporton the effect of initial state fluctuations and finite viscosities on the flow coefficients v2 and v3 asfunctions of transverse momentum and pseudo-rapidity.I will argue that simultaneous measurements of v2 and v3 can determine the shear viscosity-entropyratio more precisely. I will also touch uponrecent calculations of v2 and v3 for the LHC heavy ion collisions.


Spectrum of initial fluctuations in the little bangAuthor: Raju Venugopalan1

Co-authors: Francois Gelis 2; Kevin Dusling 3

1 Brookhaven National Laboratory2 CEA, Saclay3 North Carolina State Univ.


We discuss an ab initio computation of the initial spectrum of fluctuations in the pre-equilibriumGlasma formed in heavy ion collisions [1]. Our result resums to all loop orders the leading unstablequantum fluctuations at early times. We showed explicitly previously for a scalar field theory [2] thataveraging over the analogous spectrum of initial fluctuations leads to hydrodynamic behavior. Thecomputation can now be carried out for QCD and we outline the algorithm for doing so. In additionto providing a mechanism for early thermalization, our result for the small fluctuation spectrum alsoenables one to compute a) key features of jet modification at early times and b) sphaleron transitionrates in the Glasma. An understanding of the latter is crucial for the charge separation mechanismin the Chiral Magnetic Effect. We relate our weak coupling albeit non-perturbative results to strongcoupling approaches to thermalization.

References:[1] K. Dusling, F. Gelis and R. Venugopalan, manuscript in preparation.[2] K. Dusling, T. Epelbaum, F. Gelis and R. Venugopalan, Nucl. Phys. A850:69 (2011).

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The STAR Upgrade ProgramAuthor: Lijuan Ruan1



The STAR detector at RHIC collected its first events in June of 2000. The detector has been upgradedseveral times since that time and we are continuing to upgrade the system in order to enhancethe capabilities of the detector and widen the scope of the research program. In this talk, we willdiscuss the ongoing upgrades that will conclude in the period between 2011 and 2015. The list oftopics includes a detector upgrade that will enhance the pointing near the vertex for heavy flavoridentification (theHeavy Flavor Tracker (HFT)), a mid-rapidity detector at large radius to enhance particle ID in thelepton sector (the Muon Telescope Detector (MTD)), and detectors in the forward direction to enableW boson identification and asymmetry measurements (the Forward Gem Tracker (FGT)) as well asto measure spin asymmetries (the Forward Hadron Calorimeter(FHC)). A high level trigger upgrade(HLT) that allows us to make fast online trigger decisions for rare events will also be discussed. Afterdescribing the overall upgrade program, we will focus on the MTD and theHLT in order to review their progress, and first results, in more detail.

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Local baryon-strangeness correlation from hypernuclei and coa-lescence volume from light nuclei in relativistic heavy ion colli-sionsAuthor: Song Zhang1

Co-authors: Jinhui Chen 1; Yu-Gang Ma 1

1 Shanghai Institute of Applied Physics, CAS, China


The production of hypertriton and light nuclei are simulated in a dynamical coalescence model cou-pled with a multi-phase transport model (AMPT)~\citeSZhang10. The beam energy dependence ofstrangeness population factor, S3 = 3

ΛH/(3He× Λp ), is calculated to study local baryon-strangeness

correlation as a valuable tool to probe the nature of the dense matter created in relativistic heavyion collisions. We find that AMPT with string melting predicts an increase of S3 with increasingbeam energy, and is consistent with experimental data, while AMPT with only hadronic scatteringresults in a low S3 throughout the energy range from AGS to RHIC, and fails to describe the ex-perimental data. And we analyzed coalescence parameters, B2 and B3, based on the production ofdeuteron, helium-3 and proton. The coalescence parameters of B2 and B3 decrease with increas-ing of beam energy or number of participant. The value of B2 and B3 in this model are consistentwith the measurement by experiment collaboration in nucleus-nucleus collisions at different beamenergy~\citeNA49-07 or in different centralities~\citeSTAR09. The freeze-out correlation volume,V 1−Af (A is atomic number), is calculated in AMPT model. The results of coalescence parameter

and the freeze-out correlation volume follow the relation ofBA ∝ V 1−Af , which is from coalescence

mechanism and observed in experiments~\citeBAVf,STAR09,HLiu06. This beam energy and sys-tem size dependences indicate the increase of source size in more high energy collisions and in morecentral collisions.

References

\bibitemSZhang10 S. Zhang, J. H. Chen, H. Crawford et~al., Phys. Lett. B \bf 684, 224 (2010).\bibitemNA49-07 V. L. Kolesnikov (for NA59 Collaboration), J. Phys. Conf. Ser. \bf 110, 032010

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(2008) and references therein.\bibitemSTAR09 B. I. Abelev et~al. (STAR Collaboration), arXiv:0909.0566.\bibitemBAVf H. H. Gutbrod et~al., Phys. Rev. Lett. \bf 37, 667 (1976)\bibitemHLiu06 H. Liu and Z. Xu, arxiv:nucl-ex/0610035.

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Spectrum of fermion coupled with massive vector boson at finitetemperature in gauge invariant formalismAuthor: Daisuke Satow1

Co-authors: Teiji Kunihiro 2; Yoshimasa Hidaka 3

1 Kyoto university2 Kyoto University3 RIKEN


We investigate the massless fermion spectral function coupled with a massive vector boson (mass:m) in the whole region of temperature (T) [1]. The massive vector boson is described as a U(1)gauge boson so that we can analyze the extremely high-T region where T/m ≫ 0, in contrast to theProca formalism [2]. We show that a novel peak appears in the fermion spectral function for T~min addition to the two peaks corresponding to the normal fermionic and anti-plasmino excitationsobtained in the m=0 case [3].We find that the novel peak seems to persist though with a small strengtheven for T≫m, where the other two peaks remains robust and are smoothly connected to thoseobtained in the HTL approximation.Since our model has a U(1) gauge invariance, the poles of the fermion propagator must be gaugeinvariant. We have confirmed the gauge invariance of the poles for T≪m and T~m, while the gaugeinvariance of the poles are satisfied only for a restricted region of the gauge-fixing parameter forT≫m. We explicitly obtained the adequate region of the gauge-fixing parameter for T≫m. Ourresults shows that the unitary gauge, which corresponds to the large gauge-fixing parameter limit,is found to be inadequate for the calculation of the fermion propagator in the T≫m region, althoughthe unitary gauge is often adopted in the literature.The relevant physical systems of our analysis include the quark-gluon plasma phase near the phasetransition temperature (T_c) since vector-type collective excitation may exist there and its massmay become very small (T≫m) just above T_c. The neutrino spectrum in the early universe is alsorelevant since the neutrino couples with the massive vector particles, W and Z boson. The presentwork tells us that the analysis of the neutrino spectral function in the unitary gauge or in the Procaformalism [4] cansuffer from a strong gauge dependence in the T≫m region.

References[1] D. Satow, Y. Hidaka and T. Kunihiro, Phys. Rev. D 83,045017 (2011).[2] M. Kitazawa, T. Kunihiro and Y. Nemoto, Prog. Theor. Phys. 117, 103 (2007).[3] H. Weldon, Phys. Rev. D 26, 2789 (1982).[4] D. Boyanovsky, Phys. Rev. D 72 033004 (2005).

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Centrality dependence of viscous quark gluon plasma at LHC

Author: Asis Chaudhuri1

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Co-author: Bikash Sinha 1



Extensive analysis of RHIC data at√sNN=200 GeV Au+Au collisions has provided convincing ev-

idence that Quark Gluon Plasma (QGP) produced in such a collision behaves almost like a perfectfluid with viscosity per specific enropy η/s is around the lower bound as per AdS/CFT η/s = 1/4π.Recently, ALICE collaboration has come out with the data for elliptic flow as a function of pT as wellas the centrality dependence of charged particle multiplicity in

√sNN=2.76 TeV Pb+Pb collision [1].

Curiously enough ALICE data for charged particles can be explained by using almost the same valueof η/s ≈ 0.08 as in RHIC, except for very central collision where the data favors ideal fluid η/s ≈0rather than a viscous fluid, although energy of collision at LHC is substantially higher than RHICenergy and expected to go up still further to

√sNN=5.5 TeV.

It is also expected, in general, that η/s should go up for QGP as a function of temperature [2]. ForRHIC, it is also expected that the hadron system is more relevant than QGP, whereas, for LHC QGPviscosity should be more important than the hadronic system [3]. So, it is quite natural to ask thequestion why η/s for RHIC remain rather similar to LHC, around η/s ≈0.08.We investigate this issue and came to the inevitable conclusion that this similarity is forced upon usby the dynamics related to the geometry of the collision. For central collision or near about a valueof initial time of τi ≈=0.2 fm and a temperature of 700 MeV is quite reasonable. However, taking intoaccount peripheral collision (70-80%) one can not escape from τi ≈ 0.6 fm with initial temperatureof 500 MeV. Please note that even for τi=0.6 fm the fitted energy density remains at ~126GeV /fm3,a factor of 3.5 larger than required for RHIV energy collision.The role of peripheral collision has been overlooked by for and large; it is interesting to note that itis the peripheral collision which precipitates recent LHC data to behave rather closely to RHIC data.We need to know η/s as a function of temperature to pin point the location of phase transition orrapid cross over from hadronic to quark gluon plasma. Data even at a higher energu

√sNN=5 TeV

especially for photon and dilepton results will facilitate this idea.

[1] K. Aamodt et al, Phys. Rev. Lett. 106, 032301 (2011), arXiv:1011.3914 [nucl-ex].[2]L. P. Csernai, J. I. Kapusta and L. D. McLarren, Phys. Rev. Lett.97,152303 (1997).[3] H. Niemi, G. S. Denicol, P. Huovinen, E. Molnar, D. Rischke, arXiv:1101.2442 [nucl-th].


DynamicalK/π, p/π, andK/pfluctuations in√sNN = 7.7-200 GeV

Au+Au collisionsAuthor: Terence Tarnowsky1

1 Michigan State University


Terence J Tarnowsky (for the STAR Collaboration)

Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or chargemay be observed near a QCD critical point. Results from newmeasurements of dynamicalK/π, p/π,and K/p ratio fluctuations are presented. The commencing of a QCD critical point search at RHIChas extended the reach of possiblemeasurements of dynamicalK/π, p/π, andK/p ratio fluctuationsfrom Au+Au collisions to lower energies.

The STAR experiment has performed a comprehensive study of the energy dependence of thesedynamical fluctuations in Au+Au collisions at the energies √sNN = 7.7, 11.5, 39, 62.4, and 200 GeV.New results are compared to previous measurements and to theoretical predictions from severalmodels. The measured dynamicalK/pi fluctuations are found to be independent of collision energy,

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while dynamical p/π and K/p fluctuations have a negative value that increases toward zero at topRHIC energy.


Correlations and fluctuations from lattice QCDAuthors: Claudia Ratti1; Kalman Szabo2; Sandor Katz3; Stefan Krieg2; Szabolcs Borsanyi2; Zoltan Fodor2

1 Torino University2 Wuppertal University3 Eotvos University Budapest

We present the new results of the Wuppertal-Budapest lattice QCD collaboration on flavor diagonaland non-diagonal quark number susceptibilities with 2+1 staggered quark flavors, in a temperatureregime between 120 and 500 MeV. A Symanzik improved gauge and a stout-link improved staggeredfermion action is utilized; the light and strange quark masses are set to their physical values. Latticeswith N_t=6,8,10,12 are used.

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J/Psi production in proton-proton collisions at sqrt(s) = 2.76 TeVin the ALICE Forward Muon SpectrometerAuthor: Claudio Geuna1

1 IRFU-cea - Centre d’Etudes de Saclay


Claudio Geuna, CEA Saclay Irfu/SPhNGif-sur-Yvette, 25 March 2011

on behalf of the ALICE collaboration

Abstract

The ALICE experiment at LHC has collected, in March 2011, proton-proton data at sqrt(s) = 2.76 TeV.This energy in the center of mass allows to have a pp reference for the PbPb collisions that havebeen collected, at the end of 2010, at sqrt(sNN) = 2.76 TeV.In this poster, we show the first analysis, performed on the pp data sample at sqrt(s) = 2.76 TeV,concerning the detection of the J/ψ meson through its decay into μ+μ− pairs at forward rapidity (2.5 < y < 4 ) in the ALICE Muon Spectrometer.We focus on the different steps required to obtain the integrated and differential cross-section forinclusive J/ψ production, the latter one as a function of the J/ψ transverse momentum pT and rapidityy.First of all, details are provided concerning the criteria adopted to select runs and events used forthe analysis. The different tecniques used for the extraction of the signal are discussed as well as themethod followed to determine the acceptance and efficiency corrections.Finally, we show some preliminary plots providing also some details about the alignment of thetracking chambers of the Muon Spectrometer.

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Inhomogeneous phase during the chiral transitionAuthor: Toshitaka Tatsumi1

1 Kyoto U.


Recently there have been many works about the inhomogeneous phases accompanying the chiraltransition, which should have implications on relativistic heavy-ion collisions as well as compact-star phenomena [1].

Among them we here concentrate on the emergence and properties of a special one called dual-chiral-density wave (DCDW) state, which enjoys interesting features such as parity-violating phase,liquid-crystalline structure and spin-density wave [2]. In particular, the one-dimensional order isquasi-long-range-order in this case such that the correlation functions of scalar and pseudoscalardensities decay algebraically, as in the smectic liquid crystal[3]: fluctuations in the DCDW phaseexhibit the heterogeneous dispersion relation.The symmetry breaking pattern is also characteristic in this phase transition: U(1) subgroup of chi-ral symmetry and one-dimensional translational symmetry are broken at the same time, but is stillinvariant under the specific combination of them. So, Nambu-Goldstone modes (phasons) should ex-hibit a hybrid features of phonons and “pions”. Moreover, magnetization spatially modulates to pre-tend a spin density wave, which may be related with the magnetic activity of compact stars.

After briefly introducing DCDW in the chiral limit and discussing its salient features, we elucidatethe physical mechanism of its emergence; we emphasize differences from the usual Overhauser ef-fect or the nesting effect of the Fermi surface.Then we present a formalism to deform the original DCDW, to include the symmetry breaking ef-fect [4]. Taking a variational method we show that the deformed DCDW can be described by atopological object: it is realized by embedding the chain of the sine-Gordon kinks in 1 + 1 dimen-sion into 1 + 3 dimensional quark matter [5]. Thus we can generalize DCDW without losing thebasic concepts.

Finally we briefly discuss the neutrino emission process byway of beta decay of quarks in the DCDWphase, as a definite example of implications of DCDW on compact-star phenomena [6].

[1] D. Nickel, Phys. Rev. Lett. 103 (2009) 072301; Phys. Rev. D80 (2009) 074025.S. Carignano, D. Nickel and M Bubballa, arXiv:1007.1397.[2] T. Tatsumi and E. Nakano, hep-ph/0408294.E. Nakano and T. Tatsumi, Phys. Rev. D71 (2005) 114006.[3] G. Baym et al., Nucl. Phys. B210 (1982) 193.[4] T. Maruyama, E. Nakano and T. Tatsumi, “Ferromagnetism: Theory, Materials and Uses”, NovaPub., NY, (2011) in press.[5] V. Schoen and M. Thies, Phys. Rev. D62(2000) 096002.[6] T. Muto and T. Tatsumi, in preparation.


Spectra, flow and HBT in PbPb collisons at the LHC

Author: Piotr Bozek1

1 IFJ PAN Krakow/ Rzeszow University

The expansion of the fireball created in Pb-Pb collisions at√s = 2.76TeV is modelled using the rel-

ativistic viscous hydrodynamics. The experimentally observed interferometry radii are well repro-duced. The recent data of the ALICE Collaboration on the elliptic flow as function of the centralitycan be very well described using the hydrodynamic expansion of a fluid with a small shear viscosity

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η/s = 0.08. The elliptic flow as function of the transverse momentum shows systematic devia-tions from a hydrodynamic behavior in the small momenta region p⊥ < 800MeV. It indicates that anon-negligible contribution of non-thermalized particles from jet fragmentation is present.

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Jet quenching and elliptic flow in heavy ion collisions at RHICand LHC within a pQCD-based partonic transport modelAuthor: Oliver Fochler1

Co-authors: Carsten Greiner 1; Zhe Xu 2

1 Institut für Theoretische Physik, Goethe-Universität Frankfurt2 Frankfurt Institute for Advanced Studies


We present fully dynamic simulations of heavy ion collisions at RHIC and at LHC energies within theperturbative QCD-based partonic transport model BAMPS (Boltzmann Approach to Multi-PartonScatterings). We focus on the simultaneous investigation of high-pT observables, such as jet quench-ing, and bulk observables, such as the elliptic flow. The model features inelastic 2 <-> 3 processesbased on the Gunion-Bertsch matrix element and has recently been extended to include light quarkdegrees of freedom. This allows for direct comparison to hadronic data on the nuclear modifica-tion factor via a fragmentation scheme for high-pT partons and also allows for the discussion ofelliptic flow results in terms of a quark recombination picture. We present results on the nuclearmodification factor of neutral pions at different centralities for Au+Au collisions at RHIC energiesand compare to experimental data. First results on the nuclear modification of charged hadrons incentral Pb+Pb collisions at the LHC are also presented and compared to recent ALICE data. Fur-thermore the differential elliptic flow of gluons and quarks as well as the centrality dependence ofthe integrated elliptic flow is studied within the same framework for Au+Au at RHIC and Pb+Pb atLHC.

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Charge balance correlations and contributions to local parity vi-olation observablesAuthor: Sören Schlichting1

Co-author: Scott Pratt 2

1 Technische Universität Darmstadt2 Michigan State University


We study charged particle correlations in a thermal freeze-out model with local charge conservation.By comparison to STAR data we find that balancing charges are emitted from significantly smallerrapidity regions in central collisions compared to peripheral collisions. The results indicate thatcharge diffusion is small and the centrality dependence points to a change of the charge productionmechanism. We also calculate the contributions from charge-balance correlations to STAR’s localparity violation observable. We show how local charge conservation, when combined with ellipticflow, explains much of STAR’s measurement. In addition we show how momentum conservation,when combined with elliptic flow, induces charged particle correlations contributing to the STARmeasurement.

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Mix-ratios of Higher Order Moments of Proton and Kaon as abaseline of QCD Critical Point search at RHICAuthor: Lizhu Chen1

1 CCNU/BNL


One of the main goals of the RHIC Beam Energy Scan program is to search for the QCD critical point(CP) in the QCD phase diagram. Non-monotonic dependence of the ratios of the various momentsof conserved (such as net-charge and net-baryon) number distributions with beam energy has beenconsidered to be a signal for the CP. In addition to this, it has been recently proposed that a certainset of mix-ratios of these moments can be measured to validate the occurrence of critical phenomena.These ratios are constructed so as not to have any dependence on model parameters, including thecorrelation length. Their values after subtracting the statistical contribution should remain as unityeven in presence of CP. Measurements of these mix-ratios are a vital step towards establishing acomplete set of observables for the critical point program at RHIC. In this poster, we will present thepreliminary results of these mix-ratios using event-by-event proton and kaon multiplicity at mid-rapidity measured in Au+Au collisions at√sNN = 7.7, 11.5, 39 and 200 GeV by the STAR experiment at RHIC. It has been observed that most of

these mix-ratios are unity as a function of either the beam energy or the collision centrality.

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Centrality dependence of muon tracking efficiency in the ALICEForwardMuon Spectrometer for Pb-Pb collisions at 2.76 TeV.Author: Antoine Lardeux1

1 SUBATECH, on behalf of the ALICE collaboration


The study of the J/ψ production and open heavy flavors in central Pb-Pb collisions is a promisingtool to probe the properties of QGP in ALICE experiment at LHC.To conduct this experimental study, it is necessary to know well the response fonction of the de-tectors used, in particular, the forward muon spectrometer to detect quarkonium and heavy flavourin their muonic channel. In this sense, the tracking efficiency integrated on the five stations of thespectrometer is a critical variable. Indeed, for cross-section calculations we have to apply a correc-tion factor Acc∗ε. We use, for to evaluate this factor, realistic Monte Carlo simulations run by run.In heavy ions collisions, one of the main parameters is the centrality of the collision, directly relatedto the multiplicity and the occupancy of the detector. It is therefore crucial to know the centralitydependence of muon tracking efficiency.Another aspect of J/ψ study is to obtain its contribution to the single muon spectrum. Simulationsusing J/ψ measured cross-section, pt and y distributions, allow to obtain this contribution. Similarevaluation will be done for the vector meson in order to get rid of the resonance contribution to thesingle muon spectrum.


Event-by-event hydrodynamics and elliptic flow from fluctuat-ing initial state

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Author: Hannu Holopainen1

Co-authors: Harri Niemi 2; Kari J. Eskola 1

1 University of Jyväskylä2 Frankfurt Institute for Advanced Studies

We develop a framework for event-by-event ideal hydrodynamics to study the differential ellipticflow which is measured at different centralities in Au+Au collisions at Relativistic Heavy Ion Col-lider (RHIC). Fluctuating initial energy density profiles, which here are the event-by-event analoguesof the eWN profiles, are created using a Monte Carlo Glauber model. Using the same event planemethod for obtaining v2 as in the data analysis, we can reproduce both the measured centrality de-pendence and the pT shape of charged-particle elliptic flow up to pT ∼ 2~GeV. We also considerthe relation of elliptic flow to the initial state eccentricity using different reference planes, and dis-cuss the correlation between the physical event plane and the initial participant plane. Our resultsdemonstrate that event-by-event hydrodynamics with initial state fluctuations must be accountedfor before a meaningful lower limit for viscosity can be obtained from elliptic flow data.

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Strongly intensivemeasures for chemical fluctuations inA+Aandp+p collisions: statistical and transport models.Author: Viktor Begun1

1 Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine


The chemical fluctuations may indicate a presence and determine the position of the critical pointon a phase diagram of the QCD matter. This inspired energy and system size scan program ofNA61 collaboration at the SPS CERN and low energy scan program of STAR collaboration at theRHIC BNL. However, many other effects – fluctuations of the number of nucleon participants inA+A collisions, effects of global conservation laws, and the change in the detector acceptance withenergy – may hide or produce the fluctuation signals. All these effects are discussed in the presenttalk within statistical and transport models. Recently, the strongly intensive measures of chemicalfluctuations which are independent of volume and volume fluctuations were proposed. We calculatethese strongly intensive quantities for pions, kaons, and protons produced in A+A collisions at SPSand RHIC energies in statistical models. The results for different statistical models within grandcanonical, canonical and micro-canonical ensembles are compared with the HSD transport modelcalculations in p+p and A+A collisions. We also present the HSD model predictions for the futuremeasurements of strongly intensive quantities in p+p collisions by NA61 collaboration within theirdetector acceptances.


AAMQS: a non-linearQCDdescription of newHERAdata at small-xAuthor: Paloma Quiroga Arias1

Co-authors: Carlos Salgado 2; Guilherme Milhano 3; Javier Albacete 4; Nestor Armesto 2

1 LPTHE , UPMC Univ. Paris 62 Departamento de Fisica de Particulas and IGFAE, Universidade de Santiago de Compostela3 CENTRA, IST Lisbon and CERN TH

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4 Institut de Physique Theorique, CEA/Saclay


Recent developments in the computation of the NLO improvement for non-linear QCD evolutionequations has allowed, for the first time, for the consistent description of experimental data using afirst principle approach. In particular, the Balitsky-Kovchegov equation including running couplingeffects (rcBK) has been shown to provide an excellent global description of inclusive DIS data.I will present a global analysis of available data on inclusive structure functionsmeasured in electron-proton scattering at small values of Bjorken-x, including the latest data from the combined HERAanalysis on reduced cross sections. The resulting parametrizations allow for the reliable computationof physical observables in a kinematical region (relevant for both p-p and A-A programmes at theLHC) where the standard DGLAP based techniques are expected to fail. Also, the inclusion of theheavy quark contribution has resulted in a good description of the experimental data for the charmcomponent of the proton structure function.Further, I will discuss the kinematical domainwhere significant deviations fromNLO-DGLAP shouldbe expected and a strategy to interface this approach, reliant on k_t factorization, with the commonlyused collinearly factorized parton distribution functions. Also preliminary extensions for nuclei willbe discussed.

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Heavy quarkonium measurements from PHENIXAuthor: Abhisek Sen1

1 Georgia State University


Quarkonia suppression is one of the highly citedsignature of quark gluon plasma (QGP) formed in relativistic heavyion collisions. PHENIX observed a high suppression of J/Ψproduction in Au+Au collisions at

√s = 200 GeV. However,

theoretical predictions remain diverse due to lack of preciseknowledge of heavy flavor meson production, suppression,regeneration in hot and dense medium and other cold nucleareffects. In order to separate these effects the PHENIXcollaboration also measured J/Ψ production in d+Au collisionsat

√s = 200 GeV for isolating cold nuclear effects and Au+Au

collisions at low energies (√s = 62 GeV and 39 GeV) to study

the onset of nuclear phase transition to QGP. The idea being thatthe critical energy density for a crossover into the QGP phase maynot be reached for certain combinations. The measurement ofJ/Ψ nuclear modification factors at different center of massenergies may elucidate this transition and supplement ourunderstanding of the energy dependence of cold nuclear mattereffects. \\In this talk, we will show the latest results of J/Ψ andUpsilon measurements from p+p, d+Au collisions at

√s = 200

GeV and several energy scans of Au+Au collisions.


Jet modification from RHIC to LHCAuthor: Abhijit Majumder1

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Co-author: Chun Shen 1



We calculate the modification of hard jets in dense extended matter in thehigher-twist formalism. The single gluon emission spectrum from a hard quark due to multiplescattering in amedium is evaluated as a power series in inverse powers of the virtuality of the hard jet.Retaining corrections up to next to leading power, we calculate the medium modified fragmentationfunction by resumming the effect of multiple gluon emissions in a virtuality ordered DGLAP likeevolution equation. This new formalism is applied to the computation of the RAA in high-energyheavy-ion collisions at RHIC and LHC. The medium is modeled using viscous 2+1D fluid dynamicswhich has been tuned to describe both the spectra and the v2 at a pT < 2 GeV. The sole parameterof the calculation q is set proportional to the entropy density and is found to be approximately 2GeV2/fm at a plasma temperature of T = 350 MeV. Using this we obtain a satisfactory descriptionof the centrality and transversemomentumdependence of theRAA at RHIC aswell as its dependenceon the azimuthal angle. With no change in parameters we obtain a natural description of the risingRAA as measured by the ALICE collaboration at the LHC. Some new results from a Monte-Carloroutine based on this formalism will also be presented.

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Polarization Effects at RHIC and LHCAuthor: Celso Barros1

1 Universidade Federal de Santa Catarina


Recently, the STAR collaboration has measured the Λ and anti-Λ polarizations in 200 GeV Au-Aucollisions [1]. These results can be understood in terms of a model [2], that we proposed recently,based on the hydrodynamical model, and taking into account the effect of the final-state interac-tions (that occur in the hadronic phase) between the hyperons and other produced particles. Thesefinal interactions are described in terms of chiral effective lagrangians, that consider many hadronicprocesses. This model describes quite well the antihyperon polarization data obtained in proton-nucleus collisions, and now we extended it to study nucleus-nucleus collisions, with a very goodaccord. Theoretical results obtained with other models will also be discussed. The perspectives ofhyperon and antihyperon polarization at LHC is another subject of interest.

References:[1] STAR Collaboration: B. I. Abelev et al., Phys. Rev. C, 76, (2007) 024915.[2] C. C. Barros Jr. and Y. Hama, Phys. Lett. B., 699, 74 (2011).

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Jet Quenching via Jet CollimationAuthors: Jorge Casalderrey Solana1; José Guilherme Milhano2; Urs Wiedemann1

1 CERN PH-TH2 Instituto Superior Tecnico (IST) and CERN PH-TH


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The ATLAS and CMS Collaborations recently reported strong modifications of dijet properties inheavy ion collisions. In this work, we discuss the extent to which these first data constrain the mi-croscopic mechanism underlying jet quenching. Simple kinematic arguments lead us to identify afrequency collimation mechanism via which the medium efficiently trims away the soft componentsof the jet parton shower. Through this mechanism, the observed dijet asymmetry can be accomo-dated with values of q L that lie in the expected order of magnitude.


Can transport peak explain the low-mass enhancement of dilep-tons at RHIC?Author: Yukinao Akamatsu1

Co-authors: Hideki Hamagaki 2; Tetsufumi Hirano 3; Tetsuo Hatsuda 2

1 Nagoya University2 University of Tokyo3 Sophia University


We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIXand transport coefficients of QGP such as the charge diffusion constant D and the relaxation time\tau. The observed low-mass enhancement sets a lower-bound on the diffusion constant, D > 2/T,with T being temperature.

To reach this lower bound, we start with the second-order relativisticdissipative hydrodynamics by Israel and Stewart. The linearized hydrodynamic equation in externalelectromagnetic field gives a spectral function which is parametrized by D and \tau. Combining thespectral function with the full 3D hydrodynamic evolution, theoretical dielectron spectra and theexperimental data are compared.

Detailed analysis shows that the low-mass dilepton enhancement originates mainly from the high-temperature QGP phase where there is a large electric charge fluctuation as obtained from latticeQCD simulations.

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Higher moments of Net Kaon Fluctuation in the Beam EnergyScan of STARAuthor: AMAL SARKAR1

1 iit-bombay


The Relativistic Heavy-Ion Collider (RHIC), at BNL, has started its beam energy scan program tolocate the QCD critical point which is also one of the main aims of the STAR experiment.Calculations on the lattice predict that the higher moments of the multiplicity distribution of theconserved quantities like the net-charge, net-baryon, net-strangeness are related to the correspond-ing susceptibilities and the correlation length of the system. These moments shows deviation frommonotonic behavior at critical point. STAR experiment has already published the result for highermoments of the net-proton multiplicity distribution in Au+Au collisions at √sNN = 19.6, 62.4 and200 GeV.

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Here we report the first measurements of the standard deviation, skewness and kurtosis of the netkaon fluctuation measured by the STAR detector at mid-rapidity for Au+Au collisions at variousenergies. It will be compared with various theoretical models.

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QCD thermodynamics by numerical simulations of Lattice QCDwith Wilson-type quarksAuthor: Shinji Ejiri1

1 Niigata University


We report results on thermodynamic properties of the quark matter obtained by numerical simula-tions of lattice QCD with dynamical Wilson-type quarks. So far, most of the lattice QCD studies atfinite temperature and chemical potential have been performed using staggered-type quark actionswith the fourth-root trick for the quark determinant. To control and estimate systematic errors dueto lattice discretization, it is indispensable to carry out simulations adopting different lattice quarkactions, e.g. the Wilson-type quark action.

In this talk, we discuss the following topics performing simulations with the Iwasaki improved gaugeaction and the clover improved Wilson quark action: (1) The Equation of state computed by a fixedscale approach and a comparison with previous results by staggered quark actions. (2) The scalingproperties around the chiral phase transition point. Assuming the scaling function is the same as theO(4) spin model, we determine the phase transition line in the temperature and chemical potentialplane. (3) The quark mass dependence of the nature of the QCD transition through the histogram ofphysical quantity.

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Signals from the QCD phase transition in the early universeAuthor: Juergen Schaffner-Bielich1

Co-authors: Simon Schettler 1; Tillmann Boeckel 1



The QCD phase diagram might exhibit a first order phase transition forlarge baryochemical potentials. We explore the cosmologicalimplications of such a QCD phase transition in the early universe. Wepropose that the large baryon-asymmetry is diluted by a littleinflation where the universe is trapped in a false vacuum state ofQCD. The little inflation period will change the freeze-out criteriafor WIMP dark matter so that their annihilation and production crosssection would be reduced by orders of magnitude. In addition thepower spectrum of cold dark matter can be affected up to mass scalesof globular clusters. The effects of the QCD phase transition on therelic gravitational wave spectrum is controlled by the trace anomalyof QCD where we apply recent data from lattice gauge calculations. TheQCD transition imprints a strong step into the spectrum ofgravitational waves depending on the strength of the QCD phasetransition which could be detected with the gravitational wave

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detectors LISA, BBO and by pulsar timing. The little QCD inflationscenario could be probed with the low-energy run at BNL’s RHIC,at the heavy-ion program at GSI’s FAIR, and also at CERN’s LHC as itchanges the freeze-out criteria for WIMP dark matter.

References:Boeckel and Schaffner-Bielich, Phys. Rev. Lett. 105 (2010) 041301Schettler, Boeckel, Schaffner-Bielich, Phys. Rev. D83 (2011) 064030


Heavy ion program at JINR NICA/MPD facilityAuthor: Alexander Sorin1

Co-authors: Alexander Kovalenko 1; Grigory Trubnikov 1; IgorMeshkov 1; Richard Lednicky 1; Vladimir Kekelidze1

1 Joint Institute for Nuclear Research


New project NICA/MPD (Nuclotron-based Ion Collider fAcility/MultiPurpose Detector) is now un-der realization phase at JINR (Dubna). The main goal of the project is to start in the coming yearsan experimental study of hot and dense strongly interacting matter and search for possible signs ofthe mixed phase and critical endpoint in heavy ion collisions. This study should be carried out atcentre-of-mass ion collision energies of √sNN = 4-11 GeV (NN-equivalent) and at average luminos-ity of 10E27 cm-2 s-1 for Au (79+). The program also foresees start-up of fixed target experimentswith the extracted beams from upgraded JINR synchrotron Nuclotron at energies up to 5.81 GeV/u(scaled to A/Z = 2) and intensity up to 5*10E8 s-1 (for Au 79+). Another goal of the project is aimedto study the spin structure of nucleon and the other spin sensitive phenomena with colliding beamsof polarized protons and deuterons. The SPD (Spin Physics Detector) setup aimed at that purpose isunder design.

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J/Psi production and correlation in p+p and R_AA at high-pt inAu+Au collisionsAuthor: Zebo Tang1

1 University of Science and Technology of China


The cc bound state J/ψ provides a unique tool to probe the properties of the hot dense mediumproduced in heavy-ion collisions, but to date its production mechanism is not understood clearlyeither in heavy-ion collisions or in hadron hadron collisions. Measurement of J/ψ production athigh pT is particularly interesting since at high pT the various models give different predictions.Besides, high pT particles are widely used to study the parton-medium interactions in heavy-ioncollisions. The previous high-pT J/ψmeasurements in p+p and Cu+Cu collisions at RHIC publishedby the STAR collaboration found several interesting things, though constrained by limited statisticsand system size.

In this talk, we will present the new measurement of J/ψ → e+e− production at large pT range(0 < pT < 10GeV/c) at mid-rapidity (|y| < 1)in p+p and Au+Au collisions at 200 GeV.The datasetsare from RHIC year 2009 p+ p and 2010 Au+Au runs with significantly reduced material, the newly

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installed full TOF, and high data acquisition rates. J/ψ pT spectra and nuclear modification factorsfrom low to high pT will be discussed to understand its productionmechanism andmediummodifica-tions. The J/ψ-hadron azimuthal angle correlation in p+p collisionswill be presented to disentangleB-mesons contributions to inclusive J/ψ and study J/ψ hadronization mechanism.

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Hadron Productions at LHC Energies withHIJING2.0ModelAuthor: Wei-Tian Deng1

Co-authors: Rong Xu 2; Xin-Nian Wang 3

1 Frankfurt Institute for Advanced Studies2 IOPP3 LBNL


We updated the HIJINGMonte Carlo model with the latest parton distribution functions and new setof the parameters in the two-component-model that controls total p+p cross section and the centralpseudorapity density. We study hadron spectra and multiplicity distributions using the HIJING 2.0model and compare to recent experimental data from p + p collisions at the LHC energies. Using astrong gluon shadowing effect, we can also give the prediction about hadron production in p+Pb andPb+Pb collisions at LHC energies. The recent published LHC experiment results are in good agree-ment with our predictions within the experimental errors and theoretical uncertainties, includingthe central rapidity multiplicity and its centrality dependency in Pb+Pb collisions.

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Measurement of J/ψ photoproduction in ultra-peripheral Au+Aucollisions at √sNN=200GeV using the PHENIX detectorAuthor: Akihisa Takahara1



The idea to use the strong electromagnetic fields present in high-energy nucleusnucleus collisions to study photoproduction at hadron colliders has attractedgrowing interest in recent years.PHENIX measured J/\psi photo-production in ultra-peripheal (UPC) Au+Au collisionsat \sqrtsNN =200 GeV.We define central UPC trigger as events with no activity in the Beam-Beam Counters,but activity in ZDC and EMCal.This trigger selects the collisions with the impact parameter larger than twice the nuclearradius with a small background contribution from strong interactions. It provides a uniqueopportunity to study photo-production of hadrons by a strong electromagnetic field.

The purpose of the measurement of J/\psi photo-production cross section in ultra-peripheral colli-sionsis to probe the gluon distribution at low-x.We will report J/\psi cross section and its pT dependence measured using the high luminosity 2007data.

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Search for local strong parity violation in STAR using multipleobservablesAuthor: Dhevan Gangadharan1

1 Department of Physics-Ohio State University


Parity-odd domains fromQCD are predicted to cause charge separation of quarks across the reaction-plane created in non-central relativistic heavy ion collisions–The Chiral Magnetic Effect [1]. Herewe present several measurements to search for charge separation across the reaction-plane at STAR.We use three different observables: a three point correlator, a multiplicity asymmetry correlator,as well as a reaction-plane dependent balance function. The correlations are studied differentiallyand are presented for several Au+Au collision energies: 200, 62.4, 39, 11.5, and 7.7 GeV. We willdiscuss the sensitivities of these latest measurements to possible parity odd signals and parity evenbackgrounds.

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Vorticity and Chaos in Heavy Ion CollisionsAuthor: Alexander Sorin1

Co-author: Oleg Teryaev 1

1 Joint Institute for Nuclear Research


P-odd effects related to medium vorticity are discussed. In particular, we suggest studying a sep-aration of baryonic charge due to the large baryonic chemical potential. This separation could bemanifested in neutron asymmetries in heavy ion collisions in the FAIR and NICA energy range. Weanalyze the vorticity in various chaotic flows in detail. Chaotic flows are generalized in a nontriv-ial way relevant to heavy ion collisions. We pay special attention to their symmetry properties,both discrete and continuous. The bounds for vorticity production in heavy ion collisions are ob-tained.

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Topological interactions of non-Abelian vorticeswith quasi-particlesin high density QCDAuthor: Yuji Hirono1

Co-authors: Muneto Nitta 2; Takuya Kanazawa 3

1 The University of Tokyo2 Keio University3 Universität Regensburg

Non-Abelian vortices are topologically stable objects in the color-flavor locked (CFL) phase of denseQCD. We derive a dual Lagrangian starting with the Ginzburg-Landau effective Lagrangian for theCFL phase, and obtain topological interactions of non-Abelian vortices with quasi-particles such as

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U(1)B Nambu-Goldstone bosons (phonons) and massive gluons. We find that the phonons coupleto the translational zero modes of the vortices while the gluons couple to their orientational zeromodes in the internal space.

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J/ψ polarization in p+p collisions at√s = 200 GeV at STAR

Author: Barbara Trzeciak1

1 Warsaw University of Technology


Barbara Trzeciak for the STAR Collaboration

Currently there are many models with different assumptions regarding J/ψ production mechanismthat seem to describe the production cross section from experimental data reasonably well. Infor-mation on J/ψ spin alignment, commonly named as J/ψ polarization, may allow to discriminate J/ψproduction models. Moreover the prediction that J/ψ polarization is transverse momentum depen-dent needs to be tested.

Analysis of J/ψ polarization at mid-rapidity in p+p collisions at√s = 200 GeV registered in the STAR

experiment will be presented. Data were triggered by the STAR Electromagnetic Calorimeter. J/ψis analyzed through its dielectron decay channel. The J/ψ polarization is extracted from the decayangular distribution measured in the helicity frame.


Relativistic theory of hydrodynamic fluctuationsAuthor: Joseph Kapusta1

Co-authors: Berndt Muller 2; Misha Stephanov 3

1 University of Minnesota2 Duke University3 University of Illinois at Chicago


Hydrodynamic fluctuations have been applied to a wide variety of physical, chemical, and biologicalphenomena in the past decade. In the context of high energy heavy ion collisions, there will beintrinsic fluctuations due to the finite size and finite particle content even if the initial conditionsare fixed. We develop the theory of relativistic fluctuations, and apply it to a 1+1 dimensional boostinvariant model. In analogy to the cosmic microwave background radiation, fluctuations mightprovide information on the equation of state, including a possible critical point, and on the transportcoefficients.

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Study of Λ − Λ correlations and search for the H-dibaryon withthe STAR detector at RHIC

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Author: Neha Shah1

1 UCLA

Considerable experimental efforts have been devoted to search for theexistence of H-dibaryon, a six quark state, proposed by Jaffe[1]. It has also been proposed that theH particle would appear as a bump in theΛ−Λ invariant mass spectra if the H is a resonance state, ortheHwould lead to a depletion of the Lambda-\LambdacorrelationnearthethresholdiftheHisweaklybound.Inthisscenario, themassofHisexpectedtobeintherange(2230, 2380)MeV.Becauseofhighrateofstrangeparticleproductionperheavyioncollision,RelativisticHeavyIonCollider(RHIC)isauniqueplacetosearchfortheH−dibaryon.The\Lambda-\LambdacorrelationmeasurementsatRHICaresensitivetotheirmutualinteractions, whichcanbeusedtoprobewhetherthereisastableHparticleorHresonance.ThissensitivityisuniqueatRHICbecauseoftheallowedrangeof \Lambda-\Lambdascatteringparametersinnucleus−nucleuscollisions.Wewillpresentthemeasurementof \Lambda-\LambdacorrelationsinAu+Aucollisionsat\sqrts=39GeV and\sqrts=200$GeV using the STARexperiment at RHIC.

[1] R. L. Jaffe, Phys. Rev. Lett. 38, 195 (1977).

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Continuous Time Monte Carlo for QCD in the Strong CouplingLimitAuthor: Wolfgang Unger1

Co-author: Philippe de Forcrand 2

1 ETH Zürich2 ETH Zürich, CERN


We present results for QCD in the strong coupling limit, obtained from a worm-type algorithmon a discrete spatial lattice but with continuous Euclidean time. This is obtained by sending boththe anisotropy parameter γ2 = a/at and Nτ to infinity at fixed temperature T = γ2/Nτ . Thegain is that no continuum extrapolation for Nτ → ∞ has to be carried out. We contrast thesecomputations with those obtained on discrete lattices for large Nτ . We discuss the determinationof the critical temperature for U(3) (purely mesonic) in the chiral limit, and the extension to SU(3)(baryons included) with a baryon chemical potential.We finally discuss the possibility of a continuous time worm algorithm at finite quark mass.

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Radiative energy loss reduction in a plasma due to dampingAuthor: Marcus Bluhm1

Co-authors: Joerg Aichelin 1; Pol Bernard Gossiaux 1

1 Laboratoire SUBATECH


The strong quenching of jets and the suppression of hadron spectraat high transverse momenta are striking experimental observationsmade in high energy nuclear collisions. Both have been interpretedas signature for the formation of a deconfined plasma of QCDmatter, in which partons suffer a medium-induced energy loss. Intheoretical studies devoted to a parton’s radiative energy loss,

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however, the damping of radiation within the plasma has so farwidely been neglected.

We investigate the radiative energy loss per unit distance of arelativistic colour charge traversing as probe an infiniteabsorptive plasma. The Landau-Pomeranchuk-Migdal effect isincorporated as well as modifications due to the polarization ofand damping mechanisms in the medium. The latter arephenomenologically described by a complex index of refraction,while the colour charge dynamics is considered in the Abelianapproximation. We find a substantial reduction of the medium-induced mechanical work in addition to the well known Ter-Mikaelian effect from the polarization of matter. Moreover, theformation time of radiated quanta is also drastically reduced,both for small frequencies, where damping has a minor additionalimpact besides the polarization effect, and for larger frequencies.These effects are more pronounced for larger medium dampingand/or larger initial energy of the charge.

Therefore, we expect that our study will have a significant impacton the understanding of jet quenching phenomena in ultra-relativistic heavy-ion collisions at RHIC and even more at LHC.

Heavy flavor / 379

Heavy quark diffusion from lattice QCD spectral functionsAuthor: Heng-Tong Ding1

Co-authors: Anthony Francis 2; Wolfgang Soeldner 3

1 Brookhaven National Lab2 University of Bielefeld3 University of Regensburg


We analyze the low energy part of charmonium spectral functions on large lattices close to thecontinuum limit in the temperature region 1.5 < T/Tc < 3 as well as for T ≃ 0.75Tc. We presentevidence for the existence of a transport peak above Tc and its absence below Tc. The heavy quarkdiffusion constant is then estimated using the Kubo formula. As part of the calculation we alsodetermine the temperature dependence of the signature for the charmonium bound state in thespectral function and discuss the fate of charmonium states in the hot medium.

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Examining real-time functions on the lattice using inverse prop-agator and self-energyAuthor: Masakiyo Kitazawa1

Co-author: Masayuki Asakawa 1

1 Osaka University


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The inverse of a Euclidean correlation function has an analyticrelation to the inverse of a corresponding retardedpropagator in real time.We argue that this analyticy is exploited in the analysis ofreal-time functions with Euclidean correlator obtained inlattice QCD Monte Carlo simulations complementary tothe standard analysis of spectral functions.We analyze the inverse of quark correlator obtained on thequenched lattice, and demonstrate that the inverse correlatorcontains information to constrain the form of the quarkpropagator in real time in addition to the standard analysis.For elementary fields the inverse correlator is directlyrelated to the imaginary part of the self-energy in real time,which physically represents the rates of scattering processesdue to the optical theorem.Implications of the present analysis to these microscopicaspects of the dynamical properties are addressed.

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Local Parity Violation or Local Charge Conservation/Flow? AReaction-Plane-Dependent Balance Function StudyAuthor: Hui Wang1

1 Michigan state university


STAR has recently reported charge-dependent azimuthal correlations that are sensitive to the chargeseparation effect in Au+Au collisions at√sNN = 200 GeV [1]. Qualitatively, these results agree withsome of the theoretical predictions for local parity violation in heavy-ion collisions. However, astudy using reaction-plane-dependent balance functions shows an alternative origin of this signal.The balance function, which measures thecorrelation between oppositely charged pairs, is sensitive to the mechanisms of charge formationand the subsequent relative diffusion of the balancing charges. The reaction-plane dependent bal-ance function measurements can be related to STAR’s charge-dependent azimuthal correlations. Wereport reaction-plane-dependent balance functions for Au+Au collisions at √sNN = 200 , 62.4, 39,11.5, and 7.7 GeV using the STAR detector. The model of Schlicting and Pratt [2] incorporating localcharge conservation and elliptic flow reproduces most of the three-particle azimuthal correlationresults at 200 GeV. The experimental charge-dependent azimuthal charge correlations observed at200 GeV can be explained in terms of local charge conservation and elliptic flow.

[1] B. I. Abelev et al. [STAR Collaboration], Phys. Rev. Lett. 103, 251601 (2009) and B.I. Abelev, et al. [STAR Collaboration], Phys. Rev. C 81, 054908 (2010).[2] S. Schlichting and S. Pratt, Phys. Rev. C 83, 014913 (2011)


Eccentricity and elliptic flow in proton-proton collisions fromparton evolutionAuthor: Yoshitaka Hatta1

Co-authors: Christoffer Flensburg 2; Emil Avsar 3; Jean-Yves Ollitrault 4; Takahiro Ueda 5

1 University of Tsukuba

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2 Lund3 Penn State4 Saclay5 Karlsruhe


It has been argued that high-multiplicity proton-proton collisions at the LHC may exhibit collectivephenomena usually studied in the context of heavy-ion collisions, such as elliptic flow. We studythis issue using DIPSY, a brand-new Monte Carlo event generator which features almost-NLL BFKLdynamics and describes the transverse shape of the proton including all fluctuations. We predictthe eccentricity of the collision as a function of the multiplicity and estimate the magnitude of theelliptic flow. We then compare the result with correlation from “nonflow” effects and suggest howto suppress the latter by applying cuts in the final state.

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Light meson production in d+Au collisionsmeasured by PHENIXexperiment at sqrt(s_NN) = 200 GeVAuthor: Dmitry Kotov1

1 PNPI RAS


High pT particle suppression in heavy ion collisions appears to be one of the most exciting discov-eries at RHIC. The suppression is explained by jet-quenching via partonic energy loss in a hot anddense matter created in such collisions. Nevertheless, theoretical models tuned to describe hadronsuppression versus pT and centrality suffer from ambiguities in description of collision dynamics,parton energy loss and cold nuclear matter effects. The latter can be studied by looking at d+Aucollisions since it can be safely assumed that no hot and dense medium is being created.

The PHENIX experiment at RHIC has performed light meson production measurements in d+Aucollisions at sqrt(s_NN) = 200 GeV. This poster will deliver the latest results obtained from highstatistics 2008 data sample for omega, phi, k-short and eta-prime mesons. We will present analysesapproaches used to obtain particle yields in different hadronic and leptonic decay channels and itsnuclear modification factors. The poster will also concentrate on systematic study of neutral mesonproduction in d+Au collisions at sqrt(s_NN) = 200 GeV.

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Feasability study for a Muon Forward Tracker in ALICEAuthor: Laure Marie Massacrier1

Co-author: Antonio Uras 2

1 Institut de Physique Nucleaire de Lyon (IPNL)-Universite Claude2 Institut de physique nucléaire de Lyon


ALICE is the experiment dedicated to the study of the quark gluon plasma in heavy-ion collisionsat the LHC. Improvement of ALICE sub-detectors for the upgrade plans of the year 2017 are ongo-ing. The Muon Forward Tracker (MFT) is a proposal in view of this upgrade. The MFT is a Siliconpixels detector added in the Muon spectrometer acceptance (-4<eta<-2.5) upstream of the hadronic

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absorber. The MFT upgrade is motivated by several physics improvements. The measurement ofthe DCA (Distance of Closest Approach) of single muons and secondary vertex from dimuons willpermit the identification of open charm (ctau~ 150 microns) and beauty (ctau ~ 500 microns) mesons.The MFT, thanks to its tracking capabilities, will allow to improve the mass resolution of the res-onances for a better separation between rho/omega and phi, jpsi and psi prime,and upsilon familyresonances. In addition, it will help to reject a large fraction of muons coming from pion and kaondecays, improving the signal over background ratio. Moreover, the MFT will lead to the direct mul-tiplicity measurement, event by event, of charged particles within the spectrometer acceptance. Inorder to evaluate the feasability of this upgrade, five Silicon planes were simulated within the Ali-Root framework. Effects of multiple scattering in the absorber and L3 magnetic field on muons inthe MFT will be shown. A detailed study of the influence of the beam pipe geometry on secondaryparticles production was performed. Performances of the MFT in terms of occupancy rates in thepixel plans, secondary vertex measurement, improvement of the dimuon invariant mass resolutionwere established. Themethod used for tracking in the planes andmatching between the muon tracksand MFT tracks will also be presented.

Heavy flavor / 385

Quark recombination and heavy quark diffusion in hot nuclearmatterAuthor: Rainer Fries1

Co-authors: Min He 2; Ralf Rapp 2

1 Texas A&M University + RBRC2 Texas A&M University


We review resonance recombination for quarks and show that it is compatible with quark and hadrondistributions in local thermal equilbrium. We then calculate realistic heavy quark phase space dis-tributions in heavy ion collisions using Langevin simulations with non-perturbative interactions inhydrodynamic backgrounds. We hadronize the heavy quarks on the critical hypersurface given byhydrodynamics after constructing a criterion for the relative recombination and fragmentation con-tributions. We discuss the influence of recombination and flow on the resulting heavy meson andsingle electron R_AA and elliptic flow. We will also comment on the effect of diffusion of openheavy flavor mesons in the hadronic phase.

386

Dragging D mesons by hot hadronsAuthor: Sabyasachi Ghosh1

Co-authors: Jan-e Alam 1; Santosh K Das 1; Sourav Sarkar 1



We evaluate the drag and diffusion coefficients of a hot hadronic medium consisting of pions,nucleons, kaons and eta using open charm mesons as a probe. The interaction of the probe withthe hadronic matter has been treated in the framework of effective field theory. It is observed thatthe magnitude of both the transport coefficients are significant, indicating substantial amount ofinteraction of the heavy mesons with the thermal hadronic system. The results may have noticeableimpact on the experimental observable like the suppression of single electron spectra originatingform the decays of heavy mesons in nuclear collisions at relativistic energies.

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Towards the realization of the CBM-Micro Vertex Detector: Tech-nological challenges and detector response simulationAuthor: Christina Dritsa1

1 JLU


The future Compressed Baryonic Matter (CBM) experiment, to be operated at the FAIR facility atGSI, Darmstadt, aims at the exploration of the properties of dense baryonic matter. In particular,the search for in-medium modifications of hadrons, the study of the transition from hadronic topartonic degrees of freedom and the experimental search for a critical endpoint in the phase diagramof strongly interacting matter are among the principal physics goals of CBM.

A major challenge of CBM is to measure rare and penetrating probes such as open charm, whichis produced close to kinematical threshold at FAIR energies. Open charm identification is based ondistinguishing the displaced decay vertices from the nuclear collision vertex. This approach calls fora performant vertex detector.

The Micro Vertex Detector (MVD) proposed for CBM will consist of several layers of pixel detec-tors. Currently, the most promising candidates are Monolithic Active Pixel Sensors (MAPS) whichprovide high granularity, low material budget, good radiation hardness and relatively good readouttime.

We will present the technological challenges of the MVD and approaches towards the realization ofthe detector. A new detector response model for simulating the MAPS sensors will be presented andrelated results will be shown.


Scale for the phase diagram of quantum chromodynamicsAuthor: Sourendu Gupta1

Co-authors: Bedanga Mohanty 2; Hans George Ritter 3; Nu Xu 3; Xiaofeng Luo 4

1 TIFR, Mumbai2 VECC, Kolkata3 LBNL, Berkeley4 University of Science and Technology of China, Hefei


We present a test of QCD in the non-perturbative domain through a comparison of thermodynamicfluctuations predicted in lattice computations with the experimental data of baryon distributions inhigh-energy heavy-ion collisions. This study provides evidence for thermalization in these collisions,and allow us to set a scale for the QCD phase diagram. The scale is the temperature for the crossover from normal nuclear matter to the deconfined quark gluon plasma phase. Extension of thesetechniques might allow the identification of the critical point of QCD.

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Understanding the equilibration of matter from time-dependentcorrelator

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Author: Shu Lin1

Co-authors: Erdmenger Johanna 1; Ngo Thanh Hai 1; Shuryak Edward 2

1 MPI for Physics, Munich2 Stony Brook University


The fast thermalization of Quark Gluon Plasma, as suggested by hydrodynamical simulation, is oneof the central questions of heavy ion collisions. Theoretical understanding of the mechanism in-volves field theory out of equilibrium. While the perturbative method becomes less effective due tothe strong coupling, the gauge/gravity duality can play an important role. In [1], we studied a gravi-tational collapse model, which is dual to an equilibration process of a homogeneous QGP. We foundthat the near-equilibrium correlators of different operators approach their thermal counterpart ina universal fashion. As a first step to explore the far from equilibrium regime, we studied a modelwith a moving mirror in AdS space [2]. We solved the spatially integrated time-dependent corre-lator in the dual field theory and found that the singularities of the correlator are consistent withthe bulk-cone singularities conjecture [3]. Furthermore, we found a recursive relation among theleading order divergence of the singularities, which allow us to determine the divergences withoutsolving the correlator explicitly [4]. Possible extension to a more realistic equilibration model willbe discussed.

[1] S.~Lin and E.~Shuryak, Phys.\ Rev.\ D \bf 79 (2009) 124015[arXiv:0902.1508 [hep-th]].

[2] J.~Erdmenger, S.~Lin and T.~H.~Ngo, JHEP \bf 1104 (2011) 035arXiv:1101.5505 [hep-th].

[3] V.~E.~Hubeny, H.~Liu and M.~Rangamani, JHEP \bf 0701 (2007) 009[arXiv:hep-th/0610041].

[4] J.~Erdmenger, C.~ Hoyos, S.~Lin and T.~H.~Ngo, to appear.

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Methods for extracting elliptic flow (v2) and cocktail fits of ρ0vector-meson in STAR at RHICAuthor: Prabhat Pujahari1

1 IIT Bombay


In non-central nucleus-necleus collisions, the azimuthal angle of the outgoing particles are cor-related with the direction of the impact parameter and this phenomenon is known as anisotropicflow which is sensitive to the system properties evolved early in the collisions and hence providesevidence for the formation of a hot and dense medium created in such collisions. The measurementof elliptic flow (v2) of short-lived particles (for instance ρ0 mesons) at Relativistic Heavy Ion Colli-sions is studied through their decay products. The main focus in our study is the hadronic decaychannel of ρ0 where ρ0 → π+ +pt−. Themotivation of the ρ0 v2 measurement is to test quark number scaling as predicted by coales-cence models and to answer whether the ρ0 is directly produced or formed from pions in a hadronicphase. In this poster, we present the results of v2 for ρ0 vector mesons in Au + Au collisions at√(sNN ) = 200 GeV from STAR. We discuss the extraction of the ρ0 yield with a hadronic cocktail

fit after combinatorial background subtraction. We also discuss the invariant mass fit method usedto measure the v2 for the ρ0 mesons in the presence of large background.

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Charged Particle Ratios for p+p Collisions in √s = 62.4 GeV atRHICAuthor: Shikshit Gupta1

1 Department of Physics

The ratios of particle production in hadronic interactions are important indicators of the collisiondynamics [1]. These can be used to probe the process of hadronization in high energy collisions.We present measurements of mid-rapidity anti-particle to particle ratios in p + p collisions at √s =62.4 GeV from the STAR experiment. The measurements of the anti-particle to particle ratios arestudied as a function of transverse momentum (pT ) and comparison is made with correspondingISR results for the p + p collisions at √s = 63 GeV [2]. Identification of charged hadrons (π^± , k^± ,p and pbar) was done primarily through time projection chamber measurements. Charged hadronsare identified by using specific ionization energy loss (dE/dx)at the low momentum region [3].

References

[1] H. Satz , Rep .Prog .Phys . 63 (2000) 151.[2] B. Alper et al., NuclearPhysicsB 100 (1975) 237-290.[3] B. I. Abelev et al., [STAR Collaboration], Phys .Rev .C 79 (2009) 34909.


The thermal model on the verge of the ultimate test: the LHCdataAuthor: Anton Andronic1

Co-authors: Johanna Stachel 2; Krzysztof Redlich 3; Peter Braun-Munzinger 4

1 Gesellschaft fuer Schwerionenforschung mbH (GSI)2 University of Heidelberg3 Wroclaw University4 GSI


In our model, both the light (u,d,s) quark sector and charm(onium)have found a unified description, thus providing very differentprobes for a possible delineation of the phase boundary betweendeconfined and hadronic matter produced in nucleus-nucleus collisionsfrom low (AGS) energies up to RHIC energy.A purely thermal production (at chemical freeze-out) appears naturalfor u,d,s-carrying hadrons and a good degree of consensus has beenachieved with the RHIC data, at least for central collisions.We are rather confident in predicting the chemistry of ligh-quarkhadrons at the LHC.In contrast, charmed hadrons and charmonia can be producedat chemical freeze-out only as a result of a “distribution” intohadrons of charm quarks produced in primary hard collisions.Our model describes rather well the RHIC and SPS data on charmonia,which will be reviewed briefly.We expect that generation at the phase boundary is at the LHC theexclusive mechanism (thus lifting the present controversy whethercharmonia melt or not in the deconfined stage at RHIC and SPS

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energies).With some of the model ingredients (like the volume at chemicalfreeze-out) already constrained by the first LHC data, the mainuncertainty in our predictions remains the charm cross sectionin Pb-Pb, where shadowing is not yet known.In addition to the overall hadron abundancies, including those oflight (hyper)nuclei and their antiparticles, we provide predictionsfor charmonia and for charmed hadrons, to be confronted soon withthe LHC data.

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Dmeson reference spectra in pp collisions at√s = 2.76~TeV with

ALICEAuthor: Zaida Conesa Del Valle1

1 CERN


TheALICE experiment has the ability to measure D meson production in different colliding systems.Charm production in proton proton collisions is an important tool to test pQCD calculations in anew energy domain. Its spectrum in heavy ion interactions is influenced by the formation of hotand dense QCD matter.A common procedure to study the characteristics and effects of this matter is to compare particleproduction in heavy ion and proton proton reactions.Here we present a pQCD-based energy extrapolation of ALICE D meson pp measurements at

√s =

7~TeV to√s = 2.76~TeV, as a reference for the PbPb studies at this energy. The status of the

D0 → K− π+ analysis in pp collisions at√s = 2.76~TeV will also be described.

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Search for the QCD critical point by higher moments of the net-charge multiplicity distributionAuthor: NIHAR R SAHOO1



The Relativistic Heavy-Ion Collider (RHIC), at BNL, has undertakenits beam energy scan program in order to probe the QCD critical point. Theoretical calculationsreveal that the higher moments of the multiplicity distribution of the conserved quantities like net-charge,net-baryon, net-strangeness are related to the correspondingsusceptibilities and the correlation length of the system. Thesequantities show deviation from monotonic behavior at the CP compared to the other region.

Here we report the first measurement of the moments (standard deviation,skewness and kurtosis) ofthe net-charge multiplicity distribution measured by the STAR detector for wider range of energies.The energy and centrality dependance of these higher moments and their products will be presentedfor the 200 GeV, 39 GeV, 11.5 GeV and 7.7 GeV center of mass energies of the Au+Au collisions whichcorrespond to the baryonic chemical potential from 20MeV to 550 MeV. Theoretical predictions, con-taining the non-CP physics, from the Hadron Resonance Gas models, HIJING and UrQMD modelsare compared with the data.

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Interference effects in medium–induced gluon radiationAuthors: Edmon Iancu1; Jorge Casalderrey Solana2

1 CEA Saclay2 CERN


The recent results at the LHC on jet quenching in heavy ioncollisions call for afundamental understanding of the evolution of a relatively hard jetpropagating through a QCD medium like the quark–gluon plasma. As a firststep in that sense, we consider the interference pattern for themedium–induced gluon radiation produced by a color singletquark–antiquark antenna embedded in a QCD medium with size L.This setup is indeed well suited for studies of coherence phenomena likeangular ordering. We focus on the most favorable kinematics formedium–induced gluon radiation in the BDMPS–Z regime, that istransverse momenta k⊥ ∼

√qL, short formation

times τf ≪ L, and relatively large emission angles θgtrsimθf ≡ (q/ω)1/3 (q is the medium‘jet quenching’ parameter and ω is the gluon energy).We demonstrate that, for a dipole opening angle θqqlarger than θf , there is no interference betweenmedium–induced gluon emissions by the quark and the antiquark.That is, the in–medium contribution to the antenna pattern is theincoherent superposition of two individual BDMPS–Z spectra.Physically, this isso since, unlike the direct emissions which can be delocalized anywherethroughout the medium, the interference terms are non–zero only for thevery early emissions, such that the size of the qq dipoleat the time of emission be smaller thanthe transverse wavelength of the emitted gluon.

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Ultrasoft Fermionic Mode in QED and QCD plasmasAuthor: Yoshimasa Hidaka1

Co-author: Daisuke Satow

1 RIKEN


We discuss that the fermion spectrum at an ultrasoft energy region (≪g^2T) in quantum electrody-namics and quantum chromodynamics at high temperature T, where g is the coupling constant. Weshow that the fermion propagator has a pole at v|p|-i\gamma, where p is the momentum, v=1/3 isthe velocity, and \gamma is the damping rate of order g^2T log(1/g). The residue of the pole is weakof order g^2. When a system has conserved charges, soft modes called hydrodynamic modes appearin the bosonic sector. These hydrodynamic modes are zero mode, i.e., the dispersion of the polesis \omega=0 at p=0. The question is whether such a soft mode exists in the fermionic sector, whenthe system has a peculiar symmetry of the fermions. We show that the pole at the ultrasoft regionis related to chiral symmetry, although it is not the exact zero mode. In order to obtain the correctpole, one have to sum over relevant diagrams beyond the hard thermal loop approximation even inthe leading order of the coupling. This is similar to the calculation of transport coefficients [1]. We

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analytically obtain the pole of the fermion propagator and its residue in the leading order by solvinga Bethe-Salpeter equation. Such pole was also suggested in Ref. [2], in which the self-consistentequation was shown; however it has not been solved. We also discuss whether this phenomena isrobust in the fermion-boson system in the chiral limit.

References[1] S. Jeon, Phys. Rev. D52, 3591 (1995); Y. Hidaka and T. Kunihiro, Phys. Rev. D 83, 076004 (2011).[2] V. V. Lebedev and A. V. Smilga, Annals Phys. 202, 229 (1990).

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Measurement of J/Ψ elliptic flow inAu+Au collisions at √sNN=200GeV in STAR experimentAuthor: Hao Qiu1

1 Institute of Modern Physics

J/Ψ elliptic flow (v2) is sensitive to both the J/Ψ production mechanism and the elliptic flow of heavyquarks. While some models predict that J/Ψ produced through direct nucleon-nucleon process havevery limited v2, J/Ψ produced by the recombination of c and cbar pairs could carry finite v2, de-pending on the interaction between charm quarks and the medium. Furthermore, due to their longrelaxation time, heavy quarks are expected to thermalize much more slowly than light flavor quarks.Thus the study of J/Ψ v2 will also shed light on the extent to which the collision system is thermal-ized at RHIC.In year 2010, with the combined particle identification capability from STAR’s Time ProjectionCham-ber, Barrel Electromagnetic Calorimeter and the newly installed Time of Flight detector, STAR is ableto clearly identify electrons from J/Ψ decay over a wide momentum range. To cope with the largedata volume coming from collisions at high luminosity, a High Level online tracking Trigger wasimplemented to reconstruct J/Ψ events online and tag them for fast analysis. In addition, the lowmaterial budget in STAR setup in run 2010 allows us to dramatically improve J/Ψ identification, withunprecedented statistics. In this talk, we present J/Ψ v2(pT) measurement from 200 GeV AuAu colli-sions measured by the STAR experiment. This analysis is based on 350 million minimum bias eventsplus high tower triggered events equivalent to about 7 billion minimum bias events in the relativelyhigher transverse momentum region. The results of the collision centrality dependence of the J/Ψv2(pT) will be presented. Comparisons to models will be made and the implications on collisiondynamics at RHIC will be discussed.


Measurement of light vector mesons by PHENIX experiment atRHICAuthor: Deepali Sharma1

1 Weizmann Institute of Science


The PHENIX experiment at RHIC has carried out systematic measurements of ϕ and ω mesons inp+ p, d+Au, Cu+Cu and Au+Au collisions at √sNN = 200 GeV. Consistent results have beenobtained using leptonic and hadronic decay modes as well as different analysis techniques.

In p + p collisions, the transverse momentum distributions of ω and ϕ, as well as all other mesonsmeasured by PHENIX, are well described by the Tsallis distribution functional form. Combining thee+e− and hadronic (ω → π0gamma, π0π+π−, ϕ → K+K−) decay channels, ω and ϕ have been

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measured over a pT range of 0 - 13.5 GeV/c and 0 - 7 GeV/c respectively. New results obtained usinghadronic and dielectron channels of ω and ϕmesons in d+Au collisions extend the pT coverage to0.25 - 13 GeV/c and 0 - 7 GeV/c respectively, and reveal a moderate enhancement at intermediate pTand a hint of suppression at pT > 8 GeV/c. Both observations are consistent with previous resultsfor π0, π+ + π−,Ks andK+ +K−.

The nuclear modification factor of ω in Cu+Cu and Au+Au collisions measured over a pT rangeof 4 - 12 GeV/c, shows that ω has a similar suppression pattern as that of π0 and η, strengthening theobservation that mesons with different masses have similar behavior but different from the one ofbaryons. However, ϕ in Cu+Cu and Au+Au collisions, measured from 1 - 7 GeV/c, shows a sup-pression, that is smaller than that of the π0 and η in the intermediate pT range (2 - 5 GeV/c), whereasat higher pT , within the large experimental uncertainties, the amount of suppression appears similarto that of the light mesons. Results of ϕ production at √sNN = 62.4 GeV show a similar behaviorbut with larger uncertainties. This talk will review the most recent results obtained for light vectormesons in different collision systems and energies.

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Charmonium production on fixed target with proton and leadbeams of LHCAuthor: Alexeii Kurepin1

Co-authors: Marina Golubeva 1; Natalia Topilskaya 1

1 Institute for Nuclear Research (INR)


Charmonium production on fixed target with proton and lead beams of LHC.

A.B.Kurepin, N.S.Topilskaya, M.B.GolubevaInstitute for Nuclear Research of the Russian Academy of Sciences,117312 Moscow, Russia

Fixed target operation with proton and lead beams of LHC provides new possibilities for investigation of a mechanism of quarkonium production and suppression with good statistics at the energy interval between SPS and RHIC

The dissociation of heavy quark resonances by colour screening in a deconfined medium is one ofthe possible signature of Quark Gluon Plasma formation in high energy heavy ion collisions. Inves-tigation of charmonium production by decay on two leptons (muons) was started at the CERN SPS[1], continued at RHIC [2,3] and now is going at LHC, CERN.The theoretical models without regeneration that could reproduce SPS results produce too strongJ/ψ suppression at RHIC energies. At LHC energy a process of charmonium production is differentwith respect to the SPS and even to the RHIC. The theoretical estimates give different results, somepredict strong suppression [4], some predict enhancement [5]. In addition to prompt productionfrom hard scattering, charmonium states could be produced due to recombination which may givean enhancement instead of a suppression.The energy interval between SPS and RHIC is very important for a study of themechanism of quarko-nium production and suppression. If the proton and ion beamswill be used at LHCwith fixed targets,the energy for 7 TeV proton beam will be s = 114.6 GeV, for 2.75 TeV Pb beam s = 71.8 GeV.In order to separate normal and anomalous charmonium suppression we need to have data for ppinteraction and several target nuclei, which is easy to do with fixed target and very hard with collid-ing beams.As it was already used for the experiment on collider with a fixed target at HERA-B, the target inthe form of thin ribbon could be placed around the main orbit of LHC. The life time of the beam isdetermined by the beam-beam and beam-gas interactions. Therefore after some time the particleswill leave the main orbit and interact with the target ribbon. So for fixed target measurements onlyhalo of the beam will be used and no deterioration of the main beam will be introduced. The experi-ments at different interaction points will not feel any presence of the fixed target.In order to study a capability of using the fixed target at LHC for charmonium production we calcu-late geometrical acceptances for J/ψ production, compare acceptances at collider experiments (RHIC

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and LHC) with existing fixed target experiments. Then we estimate the counting rates and showthat J/ψ production on fixed target at LHC could be measured with rather high statistics collected inseveral days of data taking.

[1] L. Kluberg, Eur. Phys. J. C 43, 145 (2005).[2] PHENIX Collab. (A. Adare et al.), Phys. Rev. Lett. 98, 232301 (2007).[3] M. J. Leitch, J. Phys. G 34, S453 (2007).[4] R. L. Thews et al., Eur. Phys. J. C 43, 97 (2005).[5] A.Andronic, P.Braun-Munzinger, K.Redlich, J.Stachel, Phys. Lett. B571, 36-44 (2003).

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Completion ofmass production of siliconpixel ladders for PHENIXsilicon vertex tracker (VTX)Author: MAKI KUROSAWA1

1 RIKEN


The PHENIX detector had been upgraded with the silicon vertex tracker (VTX) to extend its physicscapability in both the heavy ion and spin programs at Relativistic Heavy Ion Collider (RHIC) atBrookhaven National Laboratory. The main role of VTX is precision measurement of heavy flavor.The VTX comprises a four-layer barrel detector built from two inner silicon pixel detector and twoouter silicon strip detector. A silicon pixel ladder is the basic component of a silicon pixel detector.The two inner layers of the silicon pixel detectors are made up of 30 silicon pixel ladders. Each siliconpixel detector consists of four pixel hybrid sensors, two readout buses and a support board for coolingof sensor modules. Each components are glued with epoxy resin, and the pixel hybrid sensors andreadout buses are connected electrically with bonding wires. In order to avoid increase of materialbudget, it is needed to reduce the thickness of resin. Furthermore, it is required to assemble witha precision less than 25 um. In satisfying these requirements, the mass production of silicon pixeldetectors had been successfully completed.This poster provides details of mass production of silicon pixel ladders.

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Underlying event studies in d+Au collisions at√sNN=200 GeV

from STARAuthor: Jana Bielcikova1

1 Nuclear Physics Institute ASCR


Description of heavy-ion collisions, where modifications of the fragmentation functions due to in-teraction of partons with the hot and dense medium are expected, is a challenging task and requiresa detailed understanding of small collision systems such as p+p and d+Au. Comparison of measure-ments in p+p and d+Au collisions can be further used to disentangle initial state effects from coldnuclear matter effects.

Particles produced in p+p and d+Au collisions originate not only from hard scatterings, but softand semi-hard multiple parton interactions and initial- and final-state radiation combine to produceparticles at mid-rapidity which constitute the so called underlying event. The STAR collaboration atRHIC recently presented first results on underlying event properties in p+p collisions at

√sNN=200

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GeV. We extend these studies and investigate in detail properties of underlying event in d+Au colli-sions at√sNN=200 GeV. The analysis is based on the large d+Au data sample collected by the STARexperiment in year 2008. The extracted underlying event properties are compared to those from p+pcollisions. The obtained results will serve as input to Monte Carlo models.

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Fluctuations and the Ridge from RHIC to LHCAuthor: George Moschelli1

Co-author: Sean Gavin 2

1 Frankfurt Institute for Advanced Studies2 Wayne State University


LHC and RHIC experiments exhibit a ridge-like enhancement of two particle correlations that isnarrow in relative azimuthal angle ∆ϕand broad in relative pseudorapidity∆η. Causality implies that correlations between particles sepa-rated by a large∆η must originate at the moment of production. These measurements can thereforereveal how particle production occurs. We were among the first to point out that such correlationscan emerge as a consequence of fluctuating initial conditions and the subsequent transverse expan-sion. Taking the initial fluctuations as resulting from Glasma flux tubes, we successfully describeavailable ridge measurements, including the collision energy, centrality, and transverse momentum,dependencies of the ridge amplitude and azimuthal width. The effect of initial fluctuations on jetproduction and quenching has also been studied.

In this talk we explore the impact of spatial triangularity of the Glasma flux tubes on the ∆ϕ depen-dence of two particle correlations. Our approach exploits the relationship between fluctuations andcorrelations and is compatible with multiplicity and pt fluctuation measurements. We calculate v3in our approach and compare to other model predictions. Additionally, we present our predictionfor the ridge in Pb+Pb collisions at the LHC, and compare our model to the ridge recently seen byCMS in high multiplicity 7 TeV proton-proton collisions, a measurement that could illuminate theinterplay between hard and soft particle production.

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Measurement of BaryonicResonances in ppCollisions at the LHCwith ALICEAuthors: Ayben Karasu Uysal1; Benjamin Dönigus2

1 Department of Physics, Yildiz Technical University, Istanbul, Turkey2 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm-

stadt, Germany & Helmholtz Research School H-QM, Frankfurt, Germany


The measurement of short-lived resonances allows the investigation of the collisiondynamics and of the properties of the hot and dense medium created in high-energycollisions. We study the production of the two hadronic resonances Δ++(1232) → pπ+and Λ(1520) → pK− in pp collisions at √s = 7 TeV with the ALICE apparatus at theLHC as a baseline for heavy-ion collisions. We present the performance of thereconstruction and transverse momentum spectra. The Δ++(1232)/p and Λ(1520)/Λ0

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ratios obtained from previous pp collisions and thermal model calculations are alsopresented.


Direct photon production in heavy ion collisions in PHENIX ex-periment at RHICAuthor: Edouard Kistenev1



E.Kistenev for the PHENIX Collaboration

Direct photon production in heavy ion collisions in PHENIX experiment at RHIC

Among the observables used to probe the high temperature and high density phase of heavy nucleuscollisions direct photons are considered of particular interest. At LO direct photons are producedin quark-gluon Compton scattering and quark-antiquark annihilation, the NLO processes are dom-inating in bremsstrahlung and fragmentation photon production and jet re-interaction in medium,QGP and hot hadronic stage emit thermal photons. Correlated measurements of the transverse mo-mentum dependence of direct photon production in collisions of different species and of underlyingevent observables, like isolation or flow, as well as the nuclear modification factor may give insightinto the relative contribution from various production mechanisms.

Extracting the direct photon signal from the large hadron decay background is experimentally chal-lenging particularly at lower transverse momenta and high multiplicities. PHENIX used a combi-nation of techniques based upon virtual (via low to intermediate mass e+e- pairs) and real (neutralclusters in calorimeters and reconstructed e+e- pairs from photon conversions) photon measure-ments to determine direct photon yields in the range of transverse momenta up to about 20 GeV/cfor a wide range of energies and colliding species.

In this talk we present recent PHENIX results on total direct photon production in pp, dA and AAcollisions with emphasis on azimuthal correlations and nuclear modification. Implications of thePHENIX measurements for the initial temperature and density estimates as well as for the space-time evolution of the fireball will also be discussed.

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J/\psi production at mid-rapidity in pp collisions at \sqrts=7 TeV,measured with ALICEAuthor: Ionut Cristian Arsene1

1 Gesellschaft fuer Schwerionen forschung mbH (GSI)


The J/\psi production mechanism in proton-proton collisions is not fully understood and the mea-surement of the cross-section at LHC energies will bring new constraints on theoretical models.The production of charm quarks takes place in the early collision stages. Therefore, in the case ofheavy ions, they probe the hot and dense quark-gluon medium that is expected to be formed in thecollision. The understanding of the J/\psi production in pp collisions is important also as a referencefor the same measurement in heavy ion collisions.

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We will report on the J/\psi production cross-section at mid-rapidity (|y|<0.9) in proton-proton col-lisions at \sqrts = 7 TeV measured with the ALICE detector. We will show integrated and p_tdependent cross-sections, down to p_T=0, measured using the di-electron decay channel. Compar-isons with theoretical calculations and measurements in other experiments at lower energies andthe LHC will be presented, as well as the status and prospects for the same measurement in Pb-Pbcollisions at \sqrts_NN=2.76 TeV.

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QCD critical point and event-by-event fluctuationsAuthor: Misha Stephanov1

Co-authors: Christiana Athanasiou 2; Krishna Rajagopal 2

1 UIC2 MIT


Observables measuring the magnitude and non-Gaussianity of event-by-event fluctuations can beused to discover theQCD critical point in heavy-ion collisions. I shall describe theoretical predictionsfor the non-Gaussian measures such as skewness, kurtosis and corresponding mixed moments as afunction of the beam energy in the presence of the QCD critical point. I shall discuss implicationsfor the RHIC Beam Energy Scan and what we can learn from recent data.

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Measurement of dNch/deta with the ALICE VZERO detector incentral Pb-Pb collisions at 2.76 TeVAuthor: Maxime Rene Joseph Guilbaud1

1 Institut de Physique Nucleaire de Lyon (IPNL)-Universite Claude


ALICE (A Large Ion Collider Experiment) is the LHC experiment dedicated to the study of heavy-ion collisions. The aim of ALICE is to study the properties of a state of deconfined nuclear matter,the Quark Gluon Plasma (QGP), which lattice QCD predicts to be created at the extreme temper-atures and energy densities accessible in such collisions.The VZERO detector, made of scintillatorhodoscopes on both sides of the interaction point, is covering the rapidity ranges 2.8 < eta < 5.1and −3.7 < eta < −1.7. These pseudo-rapidity ranges rely on the nominal interaction point position.Thanks to the de-bunching effect of the LHC Pb beams, the VZERO is able to measure the chargedparticles multiplicity in a large range of pseudo-rapidity (0.7 < |eta| < 5.2). In this poster, thedetector and the analysis methods are described. The corresponding results of dNch/deta measure-ments are presented.

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Reconstruction and first observation of the charmed baryon Λcin pp collisions at √s = 7 TeV with ALICEAuthor: Rosa Romita1

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ALICE is the dedicated LHC experiment to identify and characterize the quark gluon plasma in high-energy nuclear collisions. Due to their large mass and their generation at the early collision stage,heavy quarks are ideal probes. It is still an open question whether the baryon over meson enhance-ment at intermediate momentum as observed at RHIC also holds for the heavy-quark sector.We report on the analysis strategy to reconstruct the charmed baryon Λc in its hadronic decay chan-nel Λc -> p K- π+ and first results on the p-p data sample at 7 TeV recorded by the ALICE detector in2010. Both topological selections and particle identification are exploited. The Λc signal in severalpT intervals will be shown.

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Equilibration in classical Yang-Mills dynamicsAuthor: Akira Ohnishi1

Co-authors: Andreas Schafer 2; Arata Yamamoto 3; Berndt Muller 4; Teiji Kunihiro 1; Toru T. Takahashi 5

1 Kyoto University2 Regensburg University3 University of Tokyo4 Duke University5 Gunma National College of Technology


Understanding the mechanisms causing rapid thermalization deduced forhigh-energy heavy ion collisions is still a challenge.Thermalization is not fast enough in perturbative esitmate,and several instabilities in the classical Yang-Mills (CYM) equationhave been considered. In this work, we have evaluated the equilibrationtime from the chaotic behavior of CYM [1]. We have developed a method toevaluete intermediate Lyapunov exponents (ILEs) by integrating the equationof motion for an intermediate time period. Sum of positive ILEs givesthe entropy production rate in intermediate times, and is found to follow(energy density)^1/4 as expected from the scale invariance of CYM.As a phenomenological application we conclude that for pure gauge theorieswith random initial conditions thermalization occures within few fm/c,an estimate which can be reduced by the inclusion of fermions,specific initial conditions etc.

[1] T. Kunihiro, B. Muller, A. Ohnishi, A. Schafer, T.T. Takahashi, A.Yamamoto,Phys. Rev. D \bf 82 (2010), 114015 [arXiv:1008.1156].

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Critical behavior of Binder-like ratios and ratios of higher cumu-lants of conserved charges in QCD deconfinement phase transi-tionAuthor: Yuanfang Wu1

Co-authors: Lizhu Chen 1; Xiaosong Chen 2; Xue Pan 1

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1 Institute of Particle Physics, Huazhong Normal University2 Institute of Theoretial Physics, Chinese Academy of Sciences


Binder-like ratios of baryon number are firstly suggested in relativistic heavy ion collisions. Using3D-Ising(O(1)), O(2), and O(4) models, the critical behavior of Binder-like ratios and ratios of highercumulants of order parameter are fully presented. Binder-like ratio is shown to be a step functionof temperature. The critical point is the intersection of the ratios of different system sizes betweentwo platforms. From low to high temperature through the critical point, the ratios of third cumu-lants change their values from negative to positive in a valley shape, and ratios of fourth cumulantsoscillate around zero. The normalized ratios, like the Skewness and Kurtosis, do not diverge withcorrelation length, in contrary with corresponding cumulants. Applications of these characters inlocating critical point in relativistic heavy ion collisions are fully discussed.

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Identifying multi-quark hadrons from heavy ion collisionsAuthor: Sungtae Cho1

Co-authors: Akira Ohnishi 2; Che Ming Ko 3; Daisuke Jido 2; Koichi Yazaki 4; Marina Nielsen 5; Shigehiro Yasui 6;Su Houng Lee 1; Takayasu Sekihara 2; Takenori Furumoto 2; Tetsuo Hyodo 7

1 Yonsei University2 Yukawa Institiute for Theoretical Physics3 Texas A&M University4 RIKEN5 Universidada de Sao Paulo6 IPNS, KEK7 Tokyo Institute of Technology


We propose a new approach of using relativistic heavy ion collisions to identify and study multi-quark hadrons. We focus on the expected production yields of these hadrons and show that theirproduction yields are strongly affected by their internal structure [1], e.g. multi-quark configurationsor hadronic molecules.

We mainly use the coalescence model, which was successful in explaining the enhanced productionof baryons at midrapidity in the intermediate transverse momentum region [2, 3] and the quark num-ber scaling of the elliptic flow of identified hadrons [4]. Based on the coalescence model, we are ableto take into account the effects of the internal structure of hadrons, such as the angular momentumand the multiplicity of quarks [5. 6], on their production yields. We also rely on the statistical model[7], which has been known to describe the relative yields of normal hadrons very well, to extractimportant parameters for the coalescence model and normalize the expected yields.

We find that the ratio of the production yields of normal hadrons calculated in the coalescence modelto those from the statistical model, N^coal/N^stat, is in the range 0.2<N^coal/N^stat<2. Thisratio is, however, typically an order of magnitude smaller if a hadron is a compact multi-quark state.On the other hand, for a hadron which is a loosely bound hadronic molecule, it would be moreabundantly formed than the expected production yield by a factor of two and more. We furtherfind that the yields of multi-quark hadrons in relativistic heavy ion collisions are large enough fordetection in experiments. For example, the D_sJ(2317) yield per unit rapidity is predicted to bemore than 2*10^-3 in central heavy ion collisions at RHIC.Therefore, relativistic heavy ion collisionexperiments provide a promising opportunity for studying multi-quark hadrons. By measuring theirproduction yields in these experiments, we expect to achieve both new discovery of exotic hadronsand the understanding of their internal structures at the same time.

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[1] S. Cho et al. [ExHIC Collaboration] arXiv:1011.0852 [nucl-th][2] V. Greco, C. M. Ko, and P. Levai, Phys. Rev. Lett. 90, 202302 (2003), Phys. Rev. C 68, 034904(2003)[3] R.J. Fries, B. Muller, C. Nonaka, and S. A. Bass, Phys. Rev. Lett. 90, 202303 (2003), Phys. Rev. C68, 044902 (2003)[4] D. Molnar and S. A. Voloshin, Phys. Rev. Lett. 91, 092301 (2003)[5] Y. Kanada-En’yo and B. Muller, Phys. Rev. C 74, 061901(R) (2006)[6] L. W. Chen, C. M. Ko, W. Liu, and M. Nielsen, Phys. Rev. C 76, 014906 (2007)[7] A. Andronic et al. Nucl. Phys. A 772 167 (2006)

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Extended Schematic Model for Hadrons, and What Happens tothe Radius of an Excited HadronAuthor: Tamar Friedmann1

1 University of Rochester


It is well-known that making reliable predictions about low-energy QCD and hadrons is a great chal-lenge, as perturbative methods of quantum field theory do not apply when the coupling constant isstrong. The common approach has been to propose various dynamical models which are inspired byassumptions, ideas, and intuition borrowed from physical systems which are not QCD. In this talk,I present refs. 1, 2 below. I will show how a schematic model employing pure QCD ingredients canteach us about the dynamics of QCD. I will present a new extended schematic model for hadronswhere diquarks serve as building blocks on equal footing with quarks, and use it to reclassify thehadron spectrum. The outcome is that there are no radially excited mesons and no radially excitedbaryons; mesons and baryons which were believed to be radially excited are actually orbitally ex-cited states involving diquarks. The reclassification thereby provides a new set of relations betweentwo fundamental properties of hadrons: their size and their energy. The relations state that the sizeof a hadron is largest in the ground state and shrinks when the hadron is excited, contrary to prac-tically all dynamical models proposed for QCD where the quarks are allowed to be pushed apart bya centrifugal barrier or radial excitations. While this set of relations appears counter-intuitive, itprovides a novel explanation for the relationship between confinement and asymptotic freedom. Itshows that we can overcome confinement and reach asymptotic freedom by increasing a hadron’sorbital excitation: the path from confinement to asymptotic freedom is a Regge trajectory. Thissheds new light not only on the low energy regime of QCD but also on its connection with highenergies.

It is significant that the above set of relations predicts a QCD effect whereby a hadron can shrink. Itis especially important since protons and neutrons, which make up the bulk of ordinary matter, arehadrons, and as such they obey the said relations. Our prediction proved to be concrete and testablewhen it was confirmed by an experiment that showed that the size of the proton shrinks (Pohl et.al., Nature 466, 213) nine months after this work was posted.

1. T. Friedmann, “No radial excitations in low-energy QCD I: Diquarks and classification of mesons,”arXiv: 0910.2229.

2. T. Friedmann, “No radial excitations in low-energyQCD II: Shrinking radius of hadrons,” arXiv:0910.2231.


Fluctuation, dissipation, and thermalization in non-equilibriumAdS5 black hole geometries

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Author: Derek Teaney1

Co-authors: Paul Chesler 2; Simon Caron-Huot 3

1 Stony Brook University2 MIT3 Institute of Advanced Study


We give a simple recipe for computing dissipationand fluctuations (commutator and anti-commutator correlation functions) for non-equilibrium blackhole geometries. The recipeformulates Hawking radiation as an initial value problem,and is suitable for numerical work. We show how to package the fluctuation anddissipation near the event horizon into correlators on the stretched horizon.These horizon correlators determine the bulk and boundary field theorycorrelation functions.In addition, the horizon correlators are the components of a horizoneffective action which provides a quantum generalization of the membraneparadigm. In equilibrium, the analysis reproduces previous results on theBrownian motion of a heavy quark. Out of equilibrium, Wigner transforms ofcommutator and anti-commutator correlation functions obey afluctuation-dissipation relation at high frequency.

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A Forward Calorimeter (FoCal) as upgrade for the ALICE Experi-ment at CERNAuthors: Gerardus Nooren1; Martijn Reicher1; Sanjib Muhuri2; Taku Gunji3; Tomoya Tsuji3

1 Universiteit Utrecht2 Variable Energy Cyclotron Centre; Department of Atomic Energy; Government of India; 1/AF, Salt-Lake, Bidhan-

nagar; Kolkata–64.3 Center for Nuclear Study University of Tokyo

CorrespondingAuthors: [email protected], [email protected], [email protected], [email protected]

As an upgrade of the ALICE experiment at the CERN-LHC, we would like to build and install a For-ward Electromagnetic Calorimeter (FoCal) to be placed in the pseudorapidity region of 2.5 < η < 4.5,at the position of the existing PhotonMultiplicity Detector (PMD).The basic motivation of includingthe calorimeter in the forward direction is to study outstanding fundamental QCD problems at lowBjorken-x values, such as parton distributions in the nuclei, test of pQCD predictions and to probehigh temperature and high density matter in greater detail. A comprehensive measurement of p-p,p-Pb and Pb-Pb collisions at the highest LHC energies will be required. For these measurements,the detector needs to be capable of measuring photons for energies up to at least E ~200 GeV/c. Itshould allow discrimination of direct photons from neutral pions in a large momentum range andshould also provide reasonable jet energy measurements. At present, two possible designs are beingconsidered based on silicon-tungsten calorimetry. Wewill present physics motivation of this project,measurement items, conceptual detector candidates, and basic performance for the measurementsin this poster presentation.

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Nonperturbative Particle Production inBoost-Invariantly Expand-ing Electric Fields and Two-Particle Correlations

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Author: Naoto Tanji1

1 High Energy Accelerator Research Organization, KEK


Nonperturbative particle production via the Schwinger mechanism has been studied as a mechanismof matter formation in the context of heavy-ion collisions. In the color flux model, the generation oflongitudinal color-electric fields between two Lorentz-contracted nuclei receding from each otherhas been assumed. These electric fields polarize the vacuum and produce quarks and gluons. Alsoin the framework of the color glass condensate, the formation of longitudinal electric fields andlongitudinal magnetic fields as well has been predicted. One of characteristics of these electric fieldsis its boost-invariance in the longitudinal beam direction. In an ideal situation where two nucleirun at exactly the speed of light, the electric fields span only inside the forward light cone and theirconfiguration is symmetric under the longitudinal boost transformation.

We study the dynamics of nonperturbative particle pair creation in such boost-invariantly expandingelectric fields. The proper-time evolution of momentum distributions of created particles, whichpreserve the boost invariance of the background field, will be presented. The particles have thesame velocity distributions as the flow velocity of the Bjorken flow from the first instance they arecreated.

We will also present the results on the calculation of the two-particle correlation between particlesproduced in the boost-invariant field. The correlation is short-range with respect to the transversemomentum, which originates in the Bose-Einstein correlation, and is long-range with respect tothe longitudinal rapidity. This long-range rapidity correlation arises because the particles are cre-ated not as an eigenstate of a longitudinal momentum, which violates the boost-symmetry, but as asuperposition of several momentum modes preserving the boost-symmetry.

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Contribution from hard partons to the bulk elliptic flowAuthor: Boris Tomasik1

Co-author: Peter Levai 2

1 Czech Technical University in Prague - Prague - Czech Republic2 MTA KFKI RMKI


Large number of semi-hard partons deposit their energy and momentum in nuclear collisions at theLHC. Hereby they can induce collectively moving streams within the hydrodynamically behavingbulk matter. Although the production of hard partons is isotropic, in non-central collisions we havean anisotropy of their spatial distribution. We argue that via the interaction of the produced streamsthe spatial anisotropy is translated into an anisotropy of the collective expansion of the bulk matter.This is demonstrated with the help of a simple toy model. The effect is estimated to be potentiallyresponsible for about 25% of the observed elliptic flow at the LHC.

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TheALICE Inner Tracking System: performancewith proton andlead beamsAuthor: Massimo Masera1

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1 Universita degli Studi di Torino


The Inner Tracking System (ITS) of the ALICE experiment consists of six cylindrical layers of silicondetectors, exploiting three different technologies: pixel detectors for the innermost 2 layers, drift de-tectors for the two central layers and double sided strip detectors for the last two layers. Each layerhas hermetic structure in r-phi and it is coaxial with the beam pipe. The ITS covers the pseudorapid-ity range |eta|<0.9 and its distance from the nominal beam line ranges from 3.9 cm for the innermostlayer up to 43 cm for the outermost. The overall number of independent sensors is 2198 and thespatial alignment of the ITS requires the determination of about 13000 parameters. The ITS mainfunctions are those of providing both primary and secondary vertices reconstruction, of improvingthe ALICE barrel tracking capabilities in the vicinity of the interaction point and of improving themomentum resolution at high pT. Furthermore, as a standalone tracker, the ITS recovers particleswhich are missed by the external barrel detector, due to acceptance limitations.After a short summary on the status of spatial alignment and detector calibration, this talk willcover the ITS performance with p-p and Pb-Pb collisions in 2010 for what concerns vertexing andtracking.

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Hunting electrons from heavy-flavour hadron decays with theALICE Transition Radiation Detector in proton-proton collisionsat √s = 7 TeVAuthor: Markus Fasel1



The measurement of the production of heavy-flavour hadrons in proton-proton collisions is a cru-cial test for perturbative QCD. Additionally it provides the reference for heavy-flavour studies inheavy-ion collisions. Thanks to its excellent electron identification capabilities the ALICE detectoris well suited for the measurement of the open heavy-flavour cross section via single electrons. Afirst measurement of the cross section was performed with electrons identified by the ALICE TimeProjection Chamber and the Time-of-Flight detector. The Transition Radiation Detector providesa major contribution to the identification of electrons and allows to extend the inclusive electronspectrum up to transverse momenta around 10 GeV/c. During the data taking in 2010, 7 out of 18supermodules were installed, covering 340° < φ < 40° and 140° < φ < 220° and |η| < 0.9. We show theperformance of the electron identification with the Transition Radiation Detector in the analysis ofelectrons from heavy-flavour hadron decays.

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Nuclear suppression at non-zero baryonic chemical potentialAuthor: Santosh K Das1

Co-authors: Bikash Sinha 1; Jan-e Alam 1; Payal Mohanty 1



The drag and diffusion coefficients of heavy quarks propagating through abaryon rich quark gluon plasma have been calculated. The nuclear suppressionfactor, RAA for non-photonic single electron spectra resulting

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from the semileptonic decays of heavy flavour mesons have been evaluated.The role of non-zero baryonic chemical potential on RAA has beenhighlighted.


New results on event-by-event ratio fluctuations in PbPb colli-sions at CERN SPS energiesAuthor: Tim Schuster1

1 Frankfurt Institute for Advanced Studies, Goethe-University Frankfurt


Event-by-event fluctuations of hadron ratios characterize the hadro-chemical composition of thehot and dense medium created in heavy-ion collisions. This makes the fluctuation signal sensitive tochanges in the underlying structure of matter, and phase transition effects in particular. In the SPSenergy range, inclusive hadronic observables indicate the onset of the deconfinement phase tran-sition [1], making ratio fluctuations a promising observable to further characterize the transitionand possibly reveal signatures of the conjectured critical point as suggested by lattice calculationsof quark number susceptibilities at finite mu_B [2]. Kaons and protons carry large parts of the con-served quantities strangeness and baryon number. Their correlation, reflected in the kaon-to-protonratio fluctuations, is expected to undergo a significant change at the anticipated parton-hadron phaseboundary [3].Results on (K+ + K−)/(p + pbar) and K+/p fluctuations in heavy-ion collisions will be presented forthe first time. At 5 energies between sqrt(s_NN) = 6.3 and 17.3 GeV, sigma_dyn has been evaluatedin central Pb+Pb collisions. For both ratios, a fast transition from positive sigma_dyn at low SPSenergies to negative values at the higher energies is observed, an energy dependence that is notreproduced by hadronic models. While hadronic transport models predict almost constant fluctua-tions in the SPS energy range, a multiplicity scaling as suggested in [4] is also incompatible withthe data. This study is complemented by new results on the centrality dependence of ratio fluctua-tions at sqrt(s_NN) = 17.3 GeV, which confirm the systematics recently reported at RHIC energies[5].

References[1] C. Alt et al. [NA49 Collaboration], Phys. Rev. C 77, 024903 (2008) [arXiv:0710.0118 [nucl-ex]].[2] M. Cheng et al., Phys. Rev. D 79, 074505 (2009) [arXiv:0811.1006 [hep-lat]].[3] V. Koch, A. Majumder and J. Randrup, Phys. Rev. Lett. 95, 182301 (2005) [arXiv:nucl-th/0505052].[4] V. Koch and T. Schuster, Phys. Rev. C 81, 034910 (2010) [arXiv:0911.1160 [nucl-th]].[5] B. I. Abelev et al. [STAR Collaboration], Phys. Rev. Lett. 103, 092301 (2009). [arXiv:0901.1795[nucl-ex]].

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Jet studies in 200 GeV d+Au collisions from the STAR experimentat RHICAuthor: Jan Kapitan1

1 Nuclear Physics Institute ASCR


Full jet reconstruction in heavy-ion collisions is a promising tool for the quantitative study of prop-erties of the dense medium produced in heavy-ion collisions at RHIC. Jet studies in d+Au collisions

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are important to disentangle initial state nuclear effects from medium-induced kT broadening andjet quenching.We present inclusive jet pT spectra in d+Au collisions from the 2007-2008 RHIC run. We discusscorrection for detector effects and underlying event background, including systematic uncertainties.These are dominated by the Jet Energy Scale, the uncertainty of which is decreased via improveddetector response simulations.

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Charged particle production with respect to the Reaction Planein Pb-Pb collisions at

√sNN= 2.76 TeV

Author: Dong Jo Kim1



The centrality dependence of nuclear modification factor(RAA) carries information about the path-length variation of partonic energy loss. However, the inclusiveRAA for a given centrality emergesby averaging over different path lengths as the overlap zone of two colliding nuclei has typically anearly elliptical shape in the transverse plane. The partons traversing the medium in the in-plane di-rection are expected to lose less energy than out-of-plane, because they, on the average, have shorterpath length inside the medium. In this sense, azimuthal dependence of RAA w.r.t. reaction planeoffers to get a tighter constraint on the actual path length traversed by the parton in medium.

Recently we published a paper on the charged particle RAA[1], showing that the similar suppres-sion as RHIC energy is observed, and moreover a rising trend for increasing pT . Another interestingobservation is the similarity of pT -differential elliptic flow at low pT between at RHIC and the LHC[2]. Since then, we have extended the pT reach for RAA with better precision and elliptic flow mea-surement up to 20 GeV /c with event plane, which allows us to study the path-length dependenceof partonic energy loss with larger kinematic domain.

We present the latest ALICE results from Pb-Pb collisions at sqrtsNN=2.76TeV on charged particleyields with respect to reaction plane angle as a function of centrality and transverse momentum.These results allow for a detailed examination of the influence of geometry in the collision regionand of the interplay between collective flow and jet-quenching effects.

[1] ALICE, K. Aamodt et al., Phys. Lett. B696, 30 (2011), 1012.1004.[2] ALICE Collaboration, K. Aamodt et al., Phys. Rev. Lett. 105, 252301 (2010).

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Dilepton production in heavy-ion collisions within the partonhadron string dynamics (PHSD) transport approachAuthor: Olena Linnyk1

Co-authors: Elena Bratkovskaya 2; Wolfgang Cassing 1

1 University of Giessen2 FIAS, University Frankfurt am Main


We describe heavy-ion collisions from the initial phase of colliding nuclei in their groundstatesthroughout the interaction phase up to the final hadronic elastic and inelastic interactions as well

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as hadron decays using the nonequilibrium microscopic Parton-Hadron-String Dynamics (PHSD)transport approach, which includes the off-shell dynamics of quarks, antiquarks and gluons as wellas a covariant dynamical hadronization scheme in addition to the familiar (off-shell) hadronic reac-tion dynamics. Within PHSD the low mass dilepton sector (M<1 GeV) at SPS energies (measuredby the NA60 and CERES Collaborations) is rather well described by hadronic degrees of freedomwhen a collisional broadening of the vector mesons (rho, omega) is incorporated; however, this nolonger holds for higher masses. In the intermediate mass regime from 1 to 2 GeV, we find that thecontribution from ‘massive’ q+qbar annihilation in the sQGP phase dominantes over the hadronicchannels like pi+a1, pi+omega and rho+rho for In+In reactions at 160 A GeV. On the other hand, wefind a quite different pattern of the dilepton production in Au+Au collisions at the top RHIC energyof sqrt(s)=200 GeV. Here the in-medium effects for the rho and omega vector mesons do not explainthe large enhancement relative to p+p collisions observed in the invariant mass regime from 0.2 to0.6 GeV by the PHENIX Collaboration. For masses above 1 GeV at RHIC energies, we find that thedecay of open charm mesons together with the dilepton radiation from partonic interactions in thesQGP phase dominate the measured spectrum.

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Deconfinement and chiral symmetry in effectivemodelswith fermionsin higher representationsAuthor: Topi Kahara1

Co-authors: Kimmo Tuominen 1; Marco Ruggieri 2

1 Helsinki Institute of Physics2 Yukawa Institute for Theoretical Physics


We study the interaction between the chiral and deconfinement transitions using effective modelssuch as the Polyakov extended linear sigma model and the Nambu-Jona-Lasinio model. In this talkwe consider fermions in higher representations of both SU(2) and SU(3) gauge groups. Our resultsmotivate further studies of these theories on the lattice and they are also relevant for models ofelectroweak symmetry breaking utilizing new strong dynamics, and their cosmological consequences.We find that for different fermion representations the qualitative and quantitative behaviour of theorder parameters is compatible with the general expectations based on the global symmetries of theunderlying theory.

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Flow analysis with event-plane method using the VZERO detec-tor in Pb-Pb collisions at sqrt(sNN)=2.76 TeV collected by the AL-ICE experiment at the LHCAuthor: Chang Beomsu1

1 ALICE


Measurement of the azimuthal anisotropy of charged particles produced in heavy-ion collisions isone of the most powerful tools to study the properties of QCD Matter.An analysis of charged hadron flow in Pb-Pb data taken by the ALICE experiment at√sNN=2.76 TeVwill be discussed. The event plane [1] was reconstructed using the VZERO detector (two scintillatorarrays covering pseudorapidity range 2.8 < η < 5.1 and −3.7 < η < −1.7) whose large pseudorapiditygap from the central tracking system (-0.8<η<0.8) helps to reduce non-flow contributions.

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Emphasize is given to the azimuthal anisotropy of charged particles, characterized by the Fouriercoefficients, up to high transverse momenta.

[1] A. M. Poskanzer and S. A. Voloshin, Physical Review C 58, 1671-1678 (1998).

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Pion production in p+p and p+C interactions at 31 GeV/cAuthor: Antoni Aduszkiewicz1

1 Faculty of Physics, University of Warsaw


Evidence for the onset of deconfinement in central Pb+Pb collisions was reported by NA49 at theCERN SPS at collision energy 30A GeV. This observation motivated the NA61/SHINE ion programwhich, in particular, aims to study properties of the onset of deconfinement by measurements ofhadron production in p+p, p+A and nucleus-nucleus collisions at the SPS energies. The programstarted in 2009 when the on p+p interactions at 20, 31, 40, 80, and 158 GeV/c were recorded.

This contribution presents preliminary spectra of negatively charged pions produced in p+p andp+C interactions at 31 GeV/c. The NA61 results will be compared with the corresponding NA49data from central Pb+Pb collisions at this energy. Finally, the dependence of pion yield on reactiontype at 31A GeV/c (NA61 and NA49 results) and 158A GeV/c (NA49 results) will be compared anddiscussed.

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Distortion of photon HBT image by the vacuum birefringence instrong magnetic fieldAuthor: Koichi Hattori1

Co-author: Kazunori Itakura 1

1 High Energy Accelerator Research Organization (KEK)


The experiment by the ultrarelativistic heavy ion collisions has opened a novel insight into the ex-treme state of matter. Besides, it provides an opportunity to study the dynamics of strong Abelianand non-Abelian gauge fields. In peripheral collisions, an extremely strong Abelian magnetic fieldis created by two colliding heavy ions having large electric charges. The magnetic field has a muchgreater order of magnitude than those of ever observed astronomical objects.

Such a strong magnetic field becomes not only the source of an exotic phenomenon called the chiralmagnetic effect but also a background field which allows for nonlinear QED phenomena, wherethe strong magnetic field interacts with photons emitted in the early stages of time evolution ofthe created matter. Even though photon self-interaction is diagrammatically a higher order processwith a number of external photon legs intermediated by an electron loop, extraordinarily strongmagnitude of the background magnetic field compensates the smallness of the coupling constant,and leads to intriguing nonperturbative effects. The interaction causes a modification of productionand propagation of photon, which results in significant effects on the observable photon spectrum. Itwas discussed recently that the presence of magnetic fields also allows for the decay of a real photoninto a particle-antiparticle (lepton, or quark) pair, yielding an elliptic flow of observed photons [1].

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The study of such nonlinear QED phenomena provides a prevision of planned photon detection inthe LHC experiment.

In this contribution, we examine the effect of the interaction, between an emitted photon and thebackground magnetic field, on Hanbury Brown and Twiss (HBT) interferometry. Recently, one ofthe authors investigated effects of the hadronic final state mean field interaction on the pion interfer-ometry in the central collisions [2,3]. We have found therein that the HBT images are distorted dueto the phase shift of the pion amplitude propagating through the one-body mean field interactionregion, which is computed by using the semi-classical approximation. The analysis was done on thebasis of an analogue of eikonal approximation in the geometrical optics. In the present work, weincorporate the interaction of photon with the background magnetic field as a deviation of the re-fraction index from the unity, wherein the analogue is more evident. While the HBT interferometryby a photon pair is more promisingly accessible to the primordial image of the created matter thanthat by a pion pair, we have to take into account the distortion of image by the strong magneticfield.

The refraction index of the vacuum in the presence of the magnetic field is obtained by incorporatingthe self-energy of photon, resummed with respect to the number of external photon legs, into theequation of motion for the Abelian gauge field. Depending on the two physical propagating modesof photon, two distinct refraction indices, called the vacuum birefringence, are obtained. Calculat-ing the optical-path-length of the photon specified by the refraction indices, we have the imagesdistorted depending on the helicity of photons. In addition to the conventionally discussed threeHBT parameters, e.g. outward, sideward and longitudinal radii, we investigate the distortion of theoutward-sideward cross parameter, which indicates the azimuthal-angle dependence of the imagein the non-central collisions [4]. The magnitude of the distortion also depends on the azimuthalangle because the presence of the magnetic field provides a preferred orientation. We show howand to what extent the elliptic shape of the original image is distorted depending on the magnitudeof momentum, helicity and azimuthal angle.

[1] K. Tuchin, Phys. Rev. C 83, (2011), 017901[2] K. Hattori, T. Matsui, Prog. Theor. Phys. 122, (2010), 1301-1310.[3] K. Hattori, Prog. Theor. Phys. 124 (2010), 869-909.[4] M. Lisa, U. Heinz and U. Wiedemann, Phys. Lett. B 489,(2000), 287-292.

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Identified particle v3 measurements at 200GeV Au+Au collisionsat RHIC-PHENIX experimentAuthor: Sanshiro Mizuno1

1 Graduate School of Pure and Applied Sciences-University of Tsuku


Particle species dependence of transverse momentum distribution as well as elliptic event anisotropyv2 have been beautifully described by hydrodynamic model calculation in terms of radial and ellipticcollective expansion in high energy heavy ion collisions.Initial participant position fluctuation is also suggested as a source of triangular initial geometry,which could then expand collectively to form thefinal triangular event anisotropy v3 in momentum space.The first v3 measurements of identified particles at 200GeV Au+Au collisions from RHIC- PHENIXexperiment will be presented.The collective triangular expansion behavior seen in v3 will be compared with hydro-dynamic modelexpectation in order to understand possible differences or similarities from the radial and ellipticexpansion.

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Upgrade of ALICE Electromagnetic Calorimeter to enhance di-jetmeasurements

Author: Shintaro Kubota1

1 Graduate School of Pure and Applied Sciences-University of Tsukuba


Back-to-back jet produced by hard parton scatterings (di-jet) is an unique andpowerful probe to quantify the properties of Quark Gluon Plasma at LHC.In the ALICE experiment, the electromagnetic calorimeter (EMCal) providesa crucial role to reconstruct jets with a good energy resolution, together with the information byTime Projection Chamber (TPC).In order to enhance the capability of back-to-back jet identification and yields of jets, photons, π0

and their correlations,we are constructing an additional electromagnetic calorimeter, called DCal (Di-jet Calorimeter) inALICE.DCal has the same design of EMCal, but it will be placed on the opposite sideof the EMCal in azimuth at mid-rapidity −0.7η0.7, together with the Photon Spectrometer (PHOS).In this poster, we present the physics cases of DCal by using simulation data,especially on jets, di-jets, hadron(π0)-jets measurements.The current status and plan of the DCal construction, and future perspectives will be shown.


Pseudorapidity dependence of charged hadron multiplicity andtransverse energy densities in PbPb collisions from CMS

Author: Collaboration CMS1

1 UCLouvain


The pseudorapidity and centrality dependence of transverse energy and charged particle multiplic-ities offers insight into the properties of the matter produced in the collisions of ultra-relativisticheavy nuclei. Multiplicities as a function of center-of-mass energy and collision centrality are im-portant for exploring the role of hard and soft scattering in particle production and for looking atnovel effects in nucleus-nucleus collisions (e.g. scaling, saturation).

Measurements of the charged hadron multiplicity and transverse energy are presented for minimumbias PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. The number of chargedhadrons was obtained by two different methods based on the inner silicon pixel system of the CMSdetector at the LHC. One technique involved counting the number of reconstructed single particlehits in the pixel detector, while the other formed hit pairs (’tracklets’) from the different detectorlayers. The two methods are in excellent agreement. For the transverse energy measurement, CMShas almost hermetic calorimetry coverage with fine granularity and excellent resolution. In additionfor particles near central rapidity momenta from the tracker can be combined with the calorimeterdata to give a significant improvement of the system resolution. Themeasurements is comparedwithheavy-ion results from earlier experiments, where a smooth dependence on the collision energy isobserved. The results as a function of centrality are compared to the corresponding value in ppcollisions interpolated from existing CMS measurements


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Charged hadron azimuthal anisotropy (v_2) in sqrtsNN = 2.76TeV PbPb collisions from CMSCorresponding Author: [email protected]

During the past decade, azimuthal correlation measurements have played a pivotal role in our un-derstanding of the properties of high density QCDmatter through their sensitivity to the early stageevolution of relativistic heavy-ion collisions. Despite our increased understanding of the transportcoefficients of the plasma produced in these collisions, there remain many questions concerningthe interplay between initial state conditions, the equation of state, and the evolution of the systemthrough the final hadronization stage. Detailed experimental data obtained for the energy regimeaccessible using the LHC should help in establishing the shear viscosity to entropy ratio achievedin the produced, strongly interacting matter. The CMS experiment has measured the anisotropyparameter, v2, using four different methods: the event-plane, two or four particle cumulants, andLee-Yang Zeros. Consistent results are found for the different methods after considering their respec-tive sensitivities to non-flow correlations and event-by-event fluctuations in the initial conditions.The anisotropy is studied as a function of transverse momentum, pseudorapidity and centrality in abroad kinematic range: 0.3 < pT < 12.0GeV/c, |η| < 2.4, and in 12 centrality classes in the range0-80\%. The scaling of v2 with participant eccentricity and transverse particle density is examinedand compared to lower energy results.


Weak boson production measured in PbPb and pp by CMSAuthor: Collaboration CMS1

1 UCLouvain


Theunprecedented centre-of-mass energy available at the LHC offers unique opportunities for study-ing the properties of the strongly-interacting QCD matter created in PbPb collisions at extreme tem-peratures and very low parton momentum fractions. With its high precision, large acceptance fortracking and calorimetry, and a trigger scheme that allows the analysis of almost each minimumbias PbPb event by the high-level trigger, CMS is fully equipped to measure muons and electronsin the high multiplicity environment of nucleus-nucleus collisions. Electroweak boson productionis an important benchmark process at hadron colliders. Precise measurements of Z production inheavy-ion collisions can help to constrain nuclear PDFs as well as serve as a standard candle of theinitial state in PbPb collisions at the LHC energies. The inclusive and differential measurements ofthe Z boson yield in the muon decay channel will be presented, establishing that no modification isobserved with respect to next-to-leading order pQCD calculations, scaled by the number of incoher-ent nucleon-nucleon collisions. The status of the Z measurement in the electron decay channel, aswell as the first observation of W→μν in heavy ion collisions will be given. The heavy-ion resultswill be presented in the context of those obtained in pp collisions with the CMS detector.

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Centrality and transverse momentum dependence of the nuclearmodification of charged particle spectra in PbPb collisions at 2.76TeV from CMSAuthor: Collaboration CMS1

1 UCLouvain

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The nuclear modification factor R_AA is one of the key signatures for the energy loss of fast partonstraversing a QCDmedium. Charged particle transversemomentum (pT) spectra have beenmeasuredby CMS for pp collisions at sqrt(s)=0.9 and 7 TeV, corresponding to integrated luminosities of 231 ub-1 and 2.96 pb-1, respectively. Calorimeter-based high-transverse-energy jet triggers are employedto enhance the statistical reach of the high-pT measurements. The results are compared to variousgenerator tunes and also to an empirical scaling of different collision energies with xT=2pT/sqrt(s)over the pT range up to 200 GeV/c. Using a combination of xT scaling and direct interpolation atfixed pT, a reference pT spectrum at sqrt(s)=2.76 TeV is constructed from pT = 1-100 GeV/c with lessthan 13% systematic uncertainty. We have obtained R_AA in bins of collision centrality for a PbPbdata sample with an integrated luminosity of 7 ub-1, dividing by the interpolated reference spectrum.As seen at lower energies, the charged particle spectrum in central PbPb collisions is suppressed byat least a factor of five (R_AA < 0.2) compared to binary scaling around pT = 5-10 GeV/c. AbovepT = 10 GeV/c, however, there is a significant rise in the nuclear modification factor, which will bepresented out to pT = 80 GeV/c.


Measurement of inclusive isolated photons inPbPb collisionswithCMS


1 UCLouvain


In studies of the dense medium produced in ultra-relativistic heavy ion collisions, photons are im-portant hard probes, since they are not expected to be modified by the medium. Themeasurement ofisolated prompt photon production in PbPb collisions provides a test of perturbative quantum chro-modynamics (pQCD) and the information to constrain the nuclear parton distribution functions.CMS has shown excellent isolation capabilities in pp collisions at the LHC using the shower shapemethod.

In heavy-ion collisions, two independent methods, shower shape and isolation, are used to separateisolated photons from non-prompt photons. This is the first application of these pp photon isolationtechniques in heavy ion collisions. Shower shape templates are created with studies of the responsein the electromagnetic calorimeter. The latter method, based on the tracker and the calorimeter,is found to have consistent results with the former method. We report the first measurement ofthe transverse momentum spectra of isolated photons in PbPb collisions at a center-of-mass energyof 2.76 TeV per nucleon nucleon pair with the CMS detector. The results are compared to NLOcalculations at an energy of 2.76 TeV. The centrality dependence of the nuclear modification factorwill be reported for isolated prompt photons with pT from 20 GeV/c to more than 80 GeV/c.

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Rapidity and centrality dependence of transverse energy distri-butions in PbPb collisions from CMSAuthor: Collaboration CMS1

1 UCLouvain


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Transverse energy measurements offer insight into the dynamics of heavy ion collisions and thetotal entropy created. At very forward angles they may also be sensitive to the low momentumcomponents of the nuclear wave-function. CMS has almost hermetic calorimetry coverage withfine granularity and excellent resolution. In addition for particles near central rapidity momentafrom the tracker can be combined with the calorimeter data to give a significant improvement of thesystem resolution. In this talk the transverse energy measurements from 2.76 TeV PbPb collisionsas a function of centrality will be compared to similar CMS results from pp collisions and to ourrecently published multiplicity results. The pseudo rapidity dependence of the transverse energyper participant is susceptible to the longitudinal expansion of the system. This quantity has notbeen measured for truly heavy ions for centre of mass energies above 8 GeV. The width of thisdistribution grows slowly with centrality. At central rapidity the transverse energy per participantis above predictions based on lower energy data that assumed a logarithmic scaling with centre ofmass energy.

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Study of jet quenching using dijets in PbPb Collisions with CMS


1 UCLouvain


Jets are an important tool to probe the hot, dense medium that is produced in ultra-relativistic heavyion collisions. The large collision energy at the LHC provides copious production of dijets with en-ergies that can be cleanly identified above the heavy ion background. The multipurpose CompactMuon Solenoid (CMS) detector is well designed to measure these hard scattering processes with itshigh resolution calorimeters and high precision silicon tracker. Jet quenching was observed by asignificant imbalance of dijet transverse momentum in PbPb collisions at a center-of-mass energy of= 2.76 TeV. The fraction of unbalanced dijets is found to increase strongly with increasing collisioncentrality. The dijet imbalance persists to the highest jet momenta studied, while angular distribu-tions are only weakly modified. The redistribution of the quenched jet energy was studied using thetransverse momentum balance of charged tracks projected onto the direction of the leading jet. Incontrast to pp collisions, a large fraction of the momentum balance for asymmetric jets is found tobe carried by low momentum particles at large angular distance to the jet axis.

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Dijet fragmentation functions measured in PbPb collisions withCMSAuthor: Collaboration CMS1

1 UCLouvain


The energy loss of fast partons traversing the strongly interacting matter produced in high-energynuclear collisions is one of the most interesting observables to probe the nature of the producedmedium. Analyzing data from PbPb collisions at a center-of-mass energy of 2.76 TeV, recordedwith the Compact Muon Solenoid (CMS) detector, parton energy loss is observed as a significantimbalance of dijet transverse momentum. To gain further understanding of the parton energy lossmechanism and how it manifests itself in the distribution of final state particles, parton fragmen-tation functions are studied for the leading and subleading jet in bins of centrality and dijet imbal-ance.

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Dijets are reconstructed using the anti-kT jet algorithm, with the particle flow method of eventreconstruction. Particle flow, which is applied to heavy-ion collisions for the first time in this mea-surement, allows for improved jet reconstruction by combining track and calorimeter informationat the particle level. The fragmentation functions for leading and subleading jets are compared tomodel calculations and measurements in pp collisions. The results confirm and complement earlierCMS results based on calorimeter jets and yield a detailed picture of parton propagation in the hotQCD medium.

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The dynamics of quark dropletsAuthor: Johan Jannik Bjerrum-Bohr1

1 FIAS Frankfurt Institute for Advanced study


Relativistic heavy-ion collisions represent a practical way to produce Quark-Gluon Plasma in thelaboratory. The hydrodynamical model is widely used to describe the evolution of the Quark-GluonPlasma as a continuous fluid. It has been predicted that in the course of fast expansion this fluidwill split into many droplets which later on evolve by evaporating hadrons from the surface. I willpresent a simple model of a quark droplet based on the hydrodynamical description. This modelincludes collective expansion of the droplet, effects of the vacuum pressure, surface tension andhadron emission. Examples of numerical simulations will be presented.

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Monte-Carlo simulation for elastic energy loss of high-energypartons in a hydrodynamical backgroundAuthor: Jussi Auvinen1

Co-authors: Hannu Holopainen 1; Kari Eskola 1; Thorsten Renk 1


We examine the significance of elastic collisions as the suppression mechanism of high-energy par-tons in the strongly interacting medium formed in ultrarelativistic heavy ion collisions. For thispurpose, we have developed a Monte Carlo simulation describing the interactions of perturbativelyproduced, non-eikonally propagating high-energy partons with the quarks and gluons from the ex-panding QCD medium. The partonic collision rates are computed in leading-order perturbativeQCD, while three different hydrodynamical scenarios are used to model the QCD medium: (1+1)-dimensional hydro with initial conditions from the EKRT model for central heavy ion collisions,(2+1)-dimensional hydro with a smooth sWN profile obtained from the optical Glauber model fornon-central collisions, and event-by-event hydro with an eBC profile from the Monte Carlo Glaubermodel to study the initial state fluctuation effects.

We compare our results with the neutral pion suppression observed in sqrt(s_NN)=200 GeV Au+Aucollisions at the BNL-RHIC. We find the incoherent nature of elastic energy loss incompatible withthe measured data. Also the effect of the initial state fluctuations appears to be negligible.

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Jet reconstruction with particle flow in heavy-ion collisions withCMSAuthor: Collaboration CMS1

1 UCLouvain


In the particle-flow approach one attempts to combine information from all available sub-detectorsystems to reconstruct all stable particles. Such an event reconstruction has been shown to improvethe resolution of jets and missing transverse energy in pp collisions compared to purely calorimetricmeasurements. This is achieved primarily by combining the precise momentum determination ofcharged hadrons in the silicon tracker with the associated energy depositions in the calorimeters.By resolving individual particles inside jets, particle flow reduces the sensitivity of the jet energyscale to the jet fragmentation pattern, which is one of the largest sources of systematic uncertaintyin jet reconstruction. Particle flow is thus an attractive tool for the study of potential modificationsto jet fragmentation in heavy-ion collisions. The particle flow algorithm has been adapted to theheavy-ion environment. The performance of jet reconstruction from particle flow objects in PbPbcollisions using the anti-kT jet reconstruction algorithm will be presented.

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Charmonium production measured in PbPb and pp collisions byCMSAuthor: Collaboration CMS1

1 UCLouvain


CMS is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicityenvironment of nucleus-nucleus collisions. Such probes are especially relevant for studying thequark gluon plasma since they are produced at early times and propagate through the medium,mapping its evolution. In particular, the Jψ production in heavy ion collisions has been studied atdifferent energies and with different collision systems without yet giving a global picture that is fullyunderstood. Measuring the charmonium production at the LHC energies in PbPb collisions will helpconstraining predictions, in particular those expecting high recombination of prompt J/jpsis or suppression in hot medium. We will review CMS J/\psi measurements in pp collisions at√sNN = 7~TeV, which allow precision studies of quarkonia production and serve as a reference

for the observation of hot nuclear effects. CMS is able to distinguish non-prompt J/ψ from promptJ/ψ in PbPb collisions, and will present the prompt J/ψ production cross-section in PbPb inclusivelyand as a function of transverse momentum, rapidity and number of nucleons participating in thecollision. Finally, we compare the B fraction measured in PbPb collisions with that measured in ppat various energies.

Heavy flavor / 450

Bottomonium production measured in PbPb and pp collisions byCMSAuthor: Collaboration CMS1

1 UCLouvain

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The LHC centre-of-mass energy allows copious Υ production in PbPb collisions. Detailed measure-ments of bottomonium will help characterize the dense matter produced in heavy-ion collisionsbeyond what was accessible at RHIC (mostly) with charmonia. The full spectroscopy of quarko-nium states has been suggested as a possible thermometer for the QGP. With its excellent dimuonmass resolution, CMS has measured the three Υ states in pp collisions. With the 2010 PbPb datasample, CMS has observed the Υ. The Υ(1S) cross-section is presented as a function of transversemomentum, rapidity and centrality.


Observation of a ridge correlation structure in high multiplicitypp collisions with CMSAuthor: Collaboration CMS1

1 UCLouvain


Results on two-particle angular correlations are presented in proton-proton collisions at center ofmass energies of 0.9, 2.36, 2.76 and 7 TeV, over a broad range of pseudorapidity and azimuthal angle.In very high multiplicity events at 7 TeV, a pronounced structure emerges in the two-dimensionalcorrelation function for particle pairs with intermediate pT of 1-3 GeV/c, in the kinematic region2.0 < |∆η| < 4.8 and small \Delta\Phi. This structure, which has not been observed in pp collisionsbefore, is similar to what is known as the “ridge” in heavy ion collisions. It is not predicted bycommonly used proton-protonMonte Carlomodels and is not seen in lowermultiplicity pp collisions.Updated studies of this new effect as a function of particle transverse momentum, rapidity and eventcharacteristics are shown and discussed in comparison to various model calculations.


Dihadron correlations in PbPb collisions at√sNN

= 2.76 TeV withCMSAuthor: Collaboration CMS1

1 UCLouvain


Measurements of charged dihadron correlations from the CMS collaboration are presented for PbPbcollisions at a center-of-mass energy of 2.76 TeV per nucleon pair over a broad range of pseudora-pidity and the full range of azimuthal angle. With its large pseudorapidity coverage (|η|<2.4), theCMS tracker is ideally suited for detailed analyses of both short and long-range charged hadron cor-relations at the LHC. For the most central 0-5\% collisions, a broadening of the away side (∆ϕ > 1)dihadron correlation is observed at all ∆η when compared to pp collisions. A significant correlatedyield is observed for pairs of particles with small ∆ϕ but large longitudinal separation ∆η, com-monly known as the “ridge”. The ridge persists up to at least |∆η| = 4 and its effect is found tobe stronger than what was previously observed at RHIC. The dependence of the ridge region shapeand yield on transverse momentum and collision centrality has been measured. For particles oftransverse momentum of 2–4 GeV/c, the ridge is found to be the most prominent when correlated toparticles of 2–6 GeV/c, but disappears when correlated to 8–10 GeV/c particles. A Fourier analysisof the long-range two-particle correlations will be presented and discussed in the context of CMSmeasurements of higher order flow coefficients.

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Measurement of higher order flow harmonics in PbPb collisionsat √sNN = 2.76 TeV by CMS


1 UCLouvain


Collective flow is an important probe of the earliest stages in the expansion of the hot and densematter created in relativistic heavy-ion collisions. Higher harmonics of the azimuthal distributionof emitted particles, in particular v3 and v4, complement v2 measurements in elucidating the dy-namical evolution of the bulk medium and providing constraints on its transport properties. Withits large acceptance and broad rapidity coverage, the CMS detector is ideally suited to provide de-tailed analyses of higher order harmonic flow at the LHC. Measurements of vn (n = 3 to n = 6) inPbPb collisions at √sNN = 2.76 TeV using the cumulant and Lee-Yang zeros methods will be pre-sented as a function of pT and centrality. The scaling of the higher order flow harmonics with initialparticipant eccentricity and the ratios of the flow harmonics, such as v4/v22 , will be explored anddiscussed.

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Electron reconstruction and Z measurement in the di-electronchannel in PbPb collisions with CMSAuthor: Collaboration CMS1

1 UCLouvain


We report on the measurement of Z boson production and decay in the di-electron channel in Pb-Pbcollisions at sqrt(s_NN) = 2.76 TeV by the CMS experiment at the LHC. We observe about 30 eventscontaining a pair of electrons which were reconstructed to form distinctive Z boson candidates. Zboson reconstruction in the electron channel is challenging due to the complexity of electron re-construction in the high-occupancy environment of heavy-ion (HI) collisions. The reconstructionof electrons in CMS uses information from the pixel detector, the silicon strip tracker and the elec-tromagnetic calorimeter (ECAL). The measurement of electron energy in the ECAL is degraded bythe significant tracker material in front of the calorimeter, and by the presence of a strong magneticfield aligned with the beam axis, giving an azimuthal spread of electromagnetic clusters within theECAL. Despite this challenging reconstruction environment, we are able to reconstruct electronswith dedicated heavy ion tracking and tuned clustering algorithms. The performance of electronreconstruction in Pb-Pb collisions is presented. In particular, the Z measurement in the di-electronchannel is presented as a first observation and a main result of electron reconstruction in HI colli-sions.

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Study of beauty production in pp collisions at√s = 7 TeV with

ALICE, using displaced electronsAuthor: Min Jung Kweon1

1 Ruprecht-Karls-Universitaet Heidelberg

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The measurement of single electrons from heavy flavored hadron decays at RHIC indicates strongcoupling of heavy quarks to the medium produced in ultra relativistic heavy-ion collisions. At theLHC, heavy quarks are copiously produced. This will allow us to investigate the heavy quark energyloss mechanism in detail and even its quark mass dependence in the medium produced by heavy-ion collisions. Moreover, the measurement of heavy quark production in pp collisions provides animportant test of pQCD calculation and serves as a baseline for studies in heavy-ion collisions. Thebeauty quark cross section can be measured by preferentially selecting the electrons from beautyhadron decays via displaced vertices. In 2010, pp collisions at

√s = 7 TeV have been recorded by

ALICE at the LHC. We report on the status of the analysis for the measurement of the pT differentialcross section of electrons from beauty hadron decays at mid-rapidity in pp collisions.

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Readout of the CMS experiment during the 2010 heavy ion run


CMS was designed and optimized to record high luminosity pp collisions. Its powerful DAQ andtrigger systems are normally configured to handle very high frequency of relatively low multiplic-ity pp events. To reduce data volume the CMS sub-detectors are read out using zero suppressionalgorithms optimized for pp.

The large multiplicities expected in PbPb collisions required a different optimization of the zerosuppression algorithms. The optimization could only be done after the data was taken. To makesure that the collected data is of highest quality the CMS collaboration decided to disable the zerosuppression algorithms for the silicon strip tracker and the electromagnetic and hadron calorimetersfor the duration of the first PbPb run. This resulted in event size of about 12MB of data, correspondingto about 11 million channels recorded for each event. CMS was recording data at up to 180 Hz andwith a bandwidth to tape of over 2GB/s, well beyond of what it was designed for (more than 6 timesthe data volume per second recorded during the pp running).

The excellent luminosity delivered by the LHC required that CMS trigger system reduces the rate ofminimum bias events written to tape while maintaining the rate of interesting physics events. Thetrigger algorithms operating at Level-1 and High Level Trigger were optimized to provide maximumselectivity and data writing rates for jets, muons and photons. The fraction of minimum bias eventswas adjusted during running to maximize the available bandwidth.

In just few weeks CMS collected about 890 TB of data. After the run was over, CMS developed a newzero suppression algorithms optimized for heavy ions and the data was compressed offline to about190TB.

In this talk we will present the CMS configuration during the 2010 PbPb run, describe the detailedperformance of the CMS DAQ and trigger system and the subsequent offline compression process-ing.

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Performance of the CMS Zero Degree Calorimeter for PbPb andpp runningAuthor: Collaboration CMS1

1 UCLouvain


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The two CMS Zero Degree Calorimeters have been designed to measure and trigger on photonsand neutrons produced in pp and heavy ion collisions. Their trigger rate is proportional to theluminosity and can be used as a measure of beam quality. Augmented by scintillators they can alsogive a measure of the luminous region and its growth during the store. By measuring the horizontaldistribution of electromagnetic clusters they give a measure of the beam crossing angle at CMS. Wewill present their performance in test beams and in measuring the neutron spectra produced by PbPbcollisions. Finally their utility in measuring centrality will be presented.

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B → J/ψ measurement in PbPb at √s_NN = 2.76 TeV using CMS


1 UCLouvain


Measuring open heavy flavor at√(sNN ) = 2.76~TeV will test the theoretical calculations on the

J/ψ suppression at RHIC compared to LHC. With the CMS high resolution tracking, we are able toseparate prompt J/ψ from non-prompt J/ψ in heavy ion collisions, thus disentangling yield modifi-cations on primary J\ψ from those coming from Bs that decay outside the medium. The long life-timeof the b-hadron determines his decay products to be produced further away from the primary ver-tex. This makes possible the separation of the prompt from the non-prompt J/ψ based on their dis-tance to the primary vertex. To determine the fraction of non-prompt J/ψ from b-hadron decays indata, we performed a 2D unbinned maximum-likelihood fit in mass and pseudo-proper decay length,binned in transverse momentum, rapidity and centrality bins. This poster presents the first measure-ment of the prompt and non-prompt J/ψ production in the di-muon decay channel as a function oftransverse momentum, rapidity and centrality in PbPb collisions at √sNN = 2.76~TeV.

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Data-driven efficiencies for di-muon measurements in heavy ioncollisions with CMSAuthor: Collaboration CMS1

1 UCLouvain


CMS has been collecting single muon triggered data in 2010 at √sNN = 2.76~TeV in PbPb in orderto extract from real data efficiency corrections for muon based analysis. These results were used asan important cross-check for the Monte-Carlo based efficiency corrections used for the Z boson andquarkonia analysis in PbPb and taken into account in the systematics. This poster will review this \itTag and Probe technique that is used for the data-driven measurement of muon efficiencies in CMSon PbPb data. Results obtained on data are compared to what is measured on Monte-Carlo.

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Effect of the polarization on the acceptance for quarkonia studiesin PbPb at √sNN = 2.76 TeV in CMS

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1 UCLouvain


Measuring J/ψ polarization in heavy ion collisions requires a very high luminosity. While mostof the LHC experiments have been quoting corrected yields in heavy ion collisions based on theassumption of an unpolarized production, CMS prefers to quote results in different scenarios, allow-ing theorists to confront their calculations in the frame they prefer. The effect of polarization on theacceptance of quarkonia at √sNN = 2.76~TeV will be discussed in this poster. The final quarkoniacorrected yields measured by CMS in PbPb collisions for 5 different polarization scenarios will bereviewed.

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Performance of PHENIX HBD in Au + Au central collisionsAuthor: Yosuke Watanabe1

1 Tokyo University


The PHENIX experiment observed a large enhancement of electron-positronpairs in the invariant mass range of 0.2 to 0.5 GeV/c^2 in Au+Au collisionsat sqrt(s_NN)=200 GeV. However, it is difficult to draw a firm physicsconclusion from the measurement, since the measurement still has largestatistical and systematic uncertainties.The main uncertainty comes fromthe small signal-to-background ratio of about 1/200 in minimum biascollisions. The electron decay branching ratios of light vector mesonsare very small (~10^-4), while there are many background electrons mainlyoriginating from pi^0 Dalitz decays and gamma conversions.A Hadron Blind Detector,(HBD) has been installed in the PHENIX to rejectsuch background electrons using the opening angle information of electronpositron pairs, since the opening angle of electron positron pairs fromthose decays is small compared to the pairs from light vector mesons.PHENIX has successfully collected p+p and Au+Au data with the HBD in 2009 and2010.In Au+Au central collisions, high occupancy of HBD readout pads needs to behandled. The high occupancy is mainly due to the scintillation light emittedby CF4, which is the Cherenkov radiator gas of the HBD. In Au+Au peripheralcollisions or p+p collisions, the effect of scintillation light is negligiblecompared to the Cherenkov light by electrons. However, in Au+Au centralcollisions, the number of charged particles is so large that the effect ofscintillation lights becomes significant.In this poster, details of the analysis scheme to handle this situationwill be presented and current performance of HBD in di-electron measurementswill be reported.

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Quarkonia propagation and collectivity in the QGP: Towards thesuppression of quarkonia suppressionAuthor: Hamza Berrehrah1

Co-authors: Joerg Aichelin 1; Pol Bernard Gossiaux 1

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1 Subatech

For 20 years, the suppression of quarkonia has been studied as a probe of the quark gluon plasma(QGP) properties, either by Debye screening of the interaction between the q-qbar pair (Matsui andSatz) or via gluo-dissociation of quarkonia states, which remain strongly bound (Kharzeev). How-ever, the comparison between experimental data and scenarios including suppression mechanismsis not very conclusive.Rather than focusing only on these “suppressed” quarkonia, an alternative track is to focus not onlyon the suppressed but also on the physical properties of quarkonia survivors in the QGP. In fact,recent results from NA50 and NA60 experiments at SPS showed that these quarkonia indeed carrya non-zero elliptic flow. This could lead to a reconsideration of the propagation and collectivity ofthese quarkonia in the QGP, especially the elastic scattering process of quarkonia states with thepartons in the QGP.We study the quarkonia propagation and collectivity by using a hydrodynamic transport code. Thiscode requires the evaluation of two ingredients: The elastic cross section and the Fokker-Planck (FP)coefficients for stochastic processes (drag and diffusion coefficients).

In my contribution, I will first present some theoretical calculations and results obtained for theelastic cross section, following perturbative calculations in quantum mechanics and in QCD. I willthen present our model for the estimation of FP coefficients and discuss the collisional energy lossof quarkonia in the QGP. Finally, results deduced from our transport code MC@SHQ to study thequarkonia propagation and collectivity are shown. The general tendency of our results shows thatquarkonia elastic processes have non-negligible influence on the quarkonia study in theQGP.


ALICE detector upgradesAuthor: Thomas Peitzmann1

1 Universiteit Utrecht


TheALICE experiment is specifically designed for the study of strongly interacting matter as createdin heavy ion collisions at LHC. With some of its particular features, like the very good measurementof low momentum particles and the particle identification capabilities it also provides unique mea-surements in p+p collisions. However, very recent developments in heavy ion physics suggest thatsome more enhanced measurement capabilities will be strongly desirable to obtain a deeper under-standing of the new matter created.ALICE is setting up a program of detector upgrades, which could to a large extent be installed inthe long LHC shutdown foreseen for 2017/18, to address these new scientific challenges. Projectsconsidered include an upgrade of the inner tracking system (ITS), the installation of a new forwardcalorimeter (FOCAL), the extension of the muon spectrometer (MFT, muon forward tracker), theinstallation of a detector with enhanced particle identification at high momentum (VHMPID), andadditional detectors enhancing the capabilities for diffractive physics (AD = ALICE Diffractive). Anincreased rate capability of the largest detector in ALICE, the time projection chamber (TPC), is alsounder investigation, and it is foreseen to improve the data acquisition and high level trigger systems(DAQ & HLT) to achieve more bandwidth and to use more sophisticated and complex triggers. Wewill discuss the scientific frontiers and will present the corresponding upgrade projects under studyfor the ALICE experiment.

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Large-N_c behavior of hadronic models at nonzero temperature

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Author: Achim Heinz1

Co-authors: Dirk Rischke 1; Franesco Giacosa 1

1 ITP Frankfurt am Main


Effective hadronic models have been widely used to describe the chiralphase transition. In this work we study the behavior of the criticaltemperature T_c for the restoration of chiral symmetry as function ofthe number N_c of colors. We find that T_c increases with Sqrt[N_c];this scaling contradicts the basic expectations for the chiral phasetransition which, just as the deconfinement phase transition, should be independent of N_c. Indeed,in chiral models with quark degrees offreedom T_c scales as N_c^0, as expected. We have modified a hadroniclinear sigma model by including a temperature-dependent couplingconstant in such a way that the expected large-N_c scaling is recovered. Consequences for the phasediagram are investigated. Finally, we have coupled the linear sigmamodel to a Polyakov loop in sucha way that the chiral phase transition is triggered by the deconfinement phase transition. Also inthis case the correct large-N_c results are recovered.

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Construction and Installation of the PHENIX silicon pixel vertextrackerAuthor: Takashi Hachiya1

1 RIKEN


A silicon vertex tracker (VTX) is one of the upgrade programsin the PHENIX experiment to measure the production ofheavy (charm and bottom) quarks in Au+Au and polarized p+p collisions.The production of heavy quarks is a powerful toolto study both the properties of a dense partonic matter created inhigh energy heavy ion collisions and the gluon contribution tothe spin structure of proton in polarized p+p collisions.The VTX provides the precise measurement of heavy flavorsand a clear separation of charm and bottom contributions.

The VTX comprises the four layers of the barrel detectors.The two inner layers consist of silicon pixel detectorsand the two outer layers consist of silicon stripixel detectors.The VTX was constructed and installed during the shutdown periodof year 2010.In this poster presentation,we report the details of the VTX construction and installation.

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Forward and Backward to Mid-Rapidity Correlations Measuredin d+Au Collsions at

√SNN = 200 GeV with the PHENIX Detec-

tor

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Author: Zvi Citron1



Deuteron-gold collisions offer insights into the nuclear structure function and a valuable baselinefor Au+Au collisions. The d+Au system provides the opportunity to probe the gluonic structure ofthe Au nucleus. There are strong theoretical and experimental interests in the possibility of gluonsaturation effects influencing parton distributions at very low x in the nucleon. This effect wouldbe even stronger in a nucleus and can be investigated via d+Au collisions by measuring forwardrapidity, d-going side, particles. By contrast the higher x region of Au nucleus may be examinedthrough measurements of the backward rapidity, Au-going side, particles. Comparison of the mid-rapidity yield and widths correlated with jets triggered on the d going side and those correlated withjets triggered on the Au going side, allows the exploration of gluon saturation and other x dependenteffects.


Particle identification in the ALICE experimentAuthor: Alexander Philipp Kalweit1

1 Technische Universität Darmstadt


The particle identification capabilities of the ALICE experiment are unique among the four majorLHC experiments. The working principles, the strategies for signal extraction, and excellent per-formance of the central barrel detectors in a high-multiplicity environment will be presented. Theparticle identification of the Inner Tracking System (ITS) and the Time Projection Chamber (TPC) arebased on the specific energy loss whereas the Time-Of-Flight detector (TOF) determines the particlevelocity by measuring its flight time. Thus low momenta charged kaons, pions, protons, deuterons,tritons, helium-nuclei, and their respective anti-particles can be identified from 100 MeV/c up toseveral GeV/c in momentum and the corresponding spectra and yields can be extracted. Weak de-cays of strange particles can be identified via their particular kink and V0 topologies and the precisedetermination of the first and secondary vertices. The pT-reach of hadron identification can be ex-tended using Cherenkov-radiation in the High Momentum Particle Identification detector (HMPID)and by the relativistic rise in the ionizationmeasurement of the TPC. Electron identification at highermomenta is achieved by the detection of transition radiation in the Transition Radiation Detector(TRD).

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U(1)A anomaly effects on phase diagrams in chiral random ma-trix modelAuthor: Takashi Sano1

Co-author: Hirotsugu Fujii 1



Incorporating the background instanton effects, we extend the chiralrandom matrix model to include the anomaly effect.

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The anomaly effect appears naturally as the flavor mixing determinant interaction terms,which are missed in the conventional random matrix models.Due to the determinant interaction terms, the model showsthe second-order phase transition for two massless-quark flavors andthe first-order for three light-quark flavors at finite temperatures.We investigate the phase diagram of this model at finite T/mu and furthermoreat finite isospin and hypercharge chemical potentials.We find that the critical point exists on T-mu plane with physical quark masses.We also find that the determinant terms cause the mixing not only betweenthe chiral condensates but also between the chiral and meson condensates,which results in an enlargement of the region where, for example,both of the pion and the strange-quark chiral condensates have finite values.The anomaly effects enrich the phase structure andwe expect that this is also the case in QCD.

References:Phys.Rev. D80 (2009) 034007.Phys.Rev. D81 (2010) 037502.Phys.Rev. D83 (2011) 014005.

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The Level-0 trigger of the ALICE Electromagnetic Calorimeter

Author: Jiri Kral1

1 University of Jyvaskyla


The trigger system of the ALICE Electromagnetic Calorimeter (EMCal) aims to enhance the selectionof hard-QCD events containing high-p_T neutral particles and jets to be recorded. The EMCalshower (photon) trigger (level 0) entered in operation in 2010. The trigger implementation andlevel 0 decision algorithms will be presented with special focus on the tight timing requirements.Minimum bias data containing trigger decision information has been used for offline performancestudies. The trigger performance results deduced from analysis of the minimum bias data set andfrom the EMCal triggered data set taken in the p+p \sqrts=2.76TeV run will be presented.

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Charmonium spectral functions at finite momenta in the quark-gluon plasma from lattice QCDAuthor: Chiho Nonaka1

Co-authors: Masakiyo Kitazawa 2; Masayuki Asakawa 2; Yasuhiro Kohno 2

1 Nagoya University2 Osaka University


From phenomenological considerations, J/psi suppression was proposedas a signature of QGP production in relativistic heavy ion collisions,and has been considered as one of the most promising ones [1].

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However recent lattice QCD calculations show that charmonia survive even above thecritical temperature [2], which presents the possibility that the scenario of J/psisuppression in relativistic heavy ion collisions may change.To understand the relativistic heavy ion collision physics we need to take into accountdynamics of the fireball which is produced after collisions. Therefore the detailed studyon spectral functions of charmonia at finite momenta from the first principlecalculation would shed light on the understanding of the J/psi suppression mechanismin relativistic heavy ion collisions.

We study the charmonium spectral functions at finite momenta in the quark-gluonplasma on 64^3 × N_t(=96(T/Tc=0.78),54(1.38),46(1.62),40(1.87),32(2.33))quenched anisotropic lattices with anisotropy a_s /a_t= 4, analyzing correlationfunctions of charmonia by the maximum entropy method (MEM) which is avery useful and powerful tool to analyze spectral functions from lattice QCD simulations [3].We show detailed features of charmonium spectral functions of pseudoscalar andvector channels and modification of the dispersion relationat finite momenta and discuss medium effect on them in QGP.

[1] T. Matsui and H. Satz, Phys. Lett. B 178 (1986) 416,T. Hashimoto, K. Hirose, T. Kanki and O. Miyamura, Phys. Rev. Lett. 57 (1986) 2123.[2] M. Asakawa and T. Hatsuda, Phys. Rev. Lett. 92 (2004) 012001,S. Datta, F. Karsch, P. Petreczky and I. Wetzorke, Phys. Rev. D 69 (2004) 094507,H. Iida, T. Doi, N. Ishii, H. Suganuma and K. Tsumura, Phys. Rev. D 74 (2006) 074502,T. Umeda, Phys. Rev. D 75 (2007) 094502.[3] M. Asakawa, T. Hatsuda and Y. Nakahara, Prog. Part. Nucl. Phys. 46 (2001) 459.

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Heavy Quark Energy Loss in High Multiplicity Proton ProtonCollisions at LHCAuthor: Sascha Vogel1

Co-authors: Joerg Aichelin 1; Klaus Werner 1; Pol Bernard Gossiaux 1

1 Subatech

One of the most promising probes to study deconfined matter created in high energy nuclear col-lisions at RHIC and LHC is the energy loss of (heavy) quarks. It has been shown in experimentsat the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass,experience a remarkable stopping in the Quark Gluon Plasma.

In this exploratory investigation we study the energy loss of heavy quarks in high multiplicityproton-proton collisions at LHC energies. Although the colliding systems are smaller than com-pared to those at RHIC (p+p vs. Au+Au) the higher energy leads to multiplicities comparable toCu+Cu collisions at RHIC. The high energy densities reached in LHC collisions might create a de-confined state of matter even in elementary reactions. The interaction of heavy quarks with thisenvironment gives rise to a non-negligible suppression of high momentum heavy quarks in elemen-tary collisions.This probe will allow to further pin down the physical quantities of the phase transition to theQuark-Gluon-Plasma at LHC energies.

S.Vogel, P.B.Gossiaux, K.Werner, J.Aichelin,‘Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions at LHC’currently being reviewed by PRL[arXiv:1012.0764 [hep-ph]].


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Influence of tubular initial conditions on two-particle correlations

Author: Frederique Grassi1

Co-authors: Rone Andrade 1; Wei-Liang Qian 2; Yogiro Hama 1

1 Instituto de Fisica-Universidade de Sao Paulo2 Departamento de Fısica-Universidade Federal de Ouro Preto


Relativistic nuclear collisions data on two-particle correlations exhibit structures as function of rela-tive azimuthal angle and rapidity. A unified description of these near-side and awayside structuresis proposed for low to moderate transverse momentum. It is based on the combined effect of tubularinitial conditions and hydrodynamical expansion.

A 3+1 hydrodynamic approach with fluctuating tubular initial conditions, in addition to reproducingboth the near and away-side structures [1], leads to a good qualitative agreement with various data:dependence on trigger/associated particle tranverse momentum and on centrality [2], difference inthe away-side structure for in-plane/out-of plane triggers [3]. Some results on the relation betweentriangularity and triangular flow have also been obtained for this approach [4].

Since 3+1 hydrodynamics is a complicated scenario, we have also studied the effect of single tubesin 2+1 hydrodynamics. Contrary to expectations, the hydrodynamic solution shows that the highenergy density tubes (leftover from the initial particle interactions) give rise to particle emission intwo directions and this is what leads to the various structures [2], including the effect of in-plane/out-of plane triggers [3]. This description is sensitive to someof the initial tube parameters and may provide a probe of the strong interaction.

[1] J. Takahashi, B.M. Tavares, W.L.Qian, R. Andrade, F. Grassi, Y. Hama, T. Kodama, N.Xu, Phys.Rev. Lett. 103 (2009) 242301 (arXiv:0902.4870),[2] R.P.G. Andrade, F. Grassi, Y. Hama,W.-L. Qian, Nucl.Phys. A854 (2011) 81 (arXiv:1008.0139),[3] ] R.P.G. Andrade, F. Grassi, Y. Hama, W.-L. Qian, work in progress,[4] F.G. Gardim, F. Grassi, Y. Hama, M. Luzum, J.-Y. Ollitrault, work in progress.

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Using separated bottom and charm contribution to pin down therole of radiative energy loss for heavy quarksAuthor: Sascha Vogel1

Co-authors: Joerg Aichelin 1; Pol Bernard Gossiaux 1; Sonia Kabana 1; Witold Borowski 1

1 Subatech

One of the most promising probes to study deconfined matter created in high energy nuclear col-lisions at RHIC and LHC is the energy loss of (heavy) quarks. It has been shown in experimentsat the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass,experience a remarkable medium suppression in the Quark Gluon Plasma.Although various features of heavy quark physics have been understood, several challenges remain.To further study the energy loss mechanism it is not only necessary to separate charm and bottomquarks but alsoto separate the two sources of energy loss, collisional or radiative energy loss.

In this contribution we present a method for extracting the difference between collisional and radia-tive energy loss of heavy quarks.By analyzing separated bottom and charm contributions to the heavy quark spectrum one can gaininformation about the relative strength of radiative and collisional energy loss.

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This talk will give a detailed explanation of how one can separate this information experimentallyand what we can learn from this analysis with respect to heavy quark energy loss. By using existingexperimental data we will constrain the parameter space of energy loss physics and rule out severalmodel parametrizations.

A systematic parameter check with regard to RHIC data is carried out and perspectives for RHICupgrades and the LHC will be presented.


Particlemultiplicities inhigh-energyhadronic collisions atRHIC/LHCfrom CGC with local rcBK evolutionAuthor: Hirotsugu Fujii1

Co-authors: Kazunori Itakura 2; Yasushi Nara 3; Yoshio Kitadono 2

1 University of Tokyo2 KEK3 Akita Int’l University


A color glass condensate (CGC)model for particle productions at collider energies is confronted withthe data at RHIC and LHC. When applying the CGC picture to high-energy scatterings at LHC (orhigher) energies, we need to include the effects of the running coupling and the transverse expan-sion of the colliding hadrons. These two are appropriately incorporated here. Main features of ourmodel include1) fluctuations of the transverse positions of the nucleons in the projectile,2) the Gaussian shape for the transverse profile of a nucleon to account for the transverse expansionof the nucleon with increasing energy, and3) the x-evolution of the unintegrated gluon distribution by the running-coupling Balitsky-Kovchegov(rcBK) equation which is applied locally in the impact parameter space. We study the influence ofinitial condition for rcBK equation on particle production in high energy hadronic collisions. Specif-ically, the initial conditions provided by i) the naive McLerran-Venugopalan (MV) model and ii) therunning coupling MV model with adjustableparameters are examined. The use of running-coupling MV model as the initial condition is nec-essary for the consistency with the evolution equation which includes the effects of the runningcoupling.

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Global characteristics, long-range correlations, ridge and fempto-scopic radii in pp-collisions at LHCAuthor: Larisa Bravina1

Co-authors: Evgeny Zabrodin 2; Johannes Bleibel 3; Liudmila Malinina 2; Mads Stormo Nilsson 2

1 Department of Physics-University of Oslo-Unknown2 Department of Physics, University of Oslo3 Institut f\”ur Physik, Universit\”at Mainz,


Multiplicity, rapidity and transverse momentum distributions of hadrons produced in inelastic andnon-diffractive pp - collisions at energies from 200 GeV to 14 TeV are described within Quark Gluon

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String Model. Good agreement with the available experimental data, including the LHC data at√s

= 7 TeV, isobtained and predictions are made for the collisions at top LHC energy√s = 14 TeV [1]. It is shown that within the examined energy

range one cannot distinguish between the “standard” logarithmicdependence (∝ ln2 s) and novel power-law approximation(∝ Eλ), employed for particle densities and for theirmean p_T in Regge theory and in theory of Color Glass Condensate,respectively. The model indicates that Feynman scaling and extended longitudinal scaling remainvalid in the fragmentation regions, whereas strong violation of Feynman scaling is observed at midra-pidity. The KNO scaling in multiplicity distributions is violated at LHC also. The origin of bothmaintenance and violation of the scaling trends is traced to short range correlations of particles inthe strings and interplay between themulti-string processes at ultra-relativistic energies.Long-range correlations between charged particles emitted in forward(F) and backward (B) hemispheres are studied also, good agreement withdata at 546 GeV and 900 GeV is observed. The dependence looks prettylinear and its slope increases with rising energy

√s [2].

The model is able to reproduce the effect of long-range near sidecorrelations, colloquially known as ridge [3]. In contrast to the F-Bcorrelations this effect is attributed to hard Pomeron exchange andcannot be reproduced within the approach where only soft Pomerons aretaken into account. The experimental femtoscopic radii dependences are well reproduced withinQuark Gluon String Model.

[1] J.Bleibel, L.Bravina, A.Kaidalov, E.Zabrodin, arXiv:1011.2703[hep-ph]

[2] L.Bravina et al., Int. J. Mod. Phys. E (in press)

[3] L.Bravina et al., (to be submitted)

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Dimuon pairs from In-In collision at √sNN = 17.3 GeV at SPSenergiesAuthor: Jajati K. Nayak1

Co-authors: Bikash Sinha 1; Jan-e Alam 1; Sourav Sarkar 1



The invariant mass and transverse momentum spectra of lepton pairsfor In-In collision at √sNN = 17.3 GeV have been studied.We find that the broadening of the ρ mesons spectral functiondue to its interaction with the thermal baryons causes substantialexcess of dimuons at low mass region. Both the spectra agreeswell with the experimental observations made by the NA60 collaborations. We argue that the non-monotonic variation of the slope parameter extracted from the transverse mass spectra for variousinvariant massbins indicate the presence of two different phases during the evolution of thefireball.

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Nuclear suppression at large pT andxF:Direct photons fromRHICto LHCAuthor: Jan Cepila1

Co-author: Jan Nemchik 2

1 Faculty of Nuclear Sciences and Physical Engineering (FNSPE)-Czech Technical University in Prague2 IEP SAS Kosice & FNSPE CTU in Prague


We discuss a common feature of all known reactions on nuclear targets - a significant suppressionat large Feynman xF and large transverse momenta pT of produced particles. The main emphasisis devoted to production of prompt photons since they are not expected to be accompanied by anyfinal state interaction, either energy loss or absorption. Therefore, besides the Cronin enhancementat medium pT and small isotopic corrections at larger pT, one should not expect any nuclear effects.However, data from the PHENIX experiment demonstrate a significant large-pT suppression in cen-tral d+Au and Au+Au collisions that cannot be induced by coherence phenomena. We demonstratethat such an unexpected result is subject to the energy sharing problem in multiple initial state inter-actions. Using the colour dipole approach we describe first the large-pT production of direct photonsin the RHIC kinematic region in agreement with available data. We study also a rise of nuclear effectswith rapidity(xF) caused besides corrections for energy deficit by an increasing onset of coherencephenomena. In the LHC energy range we analyze relative manifestation of these effects presentingpredictions for large-pT suppression at different rapidities. We analyze also a contribution of gluonshadowing as a leading twist shadowing correction modifying nuclear effects especially at smallpT.

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Measurement of neutral mesons at ALICE by means of one pho-ton detected in electromagnetic calorimeter and another from itsconversion in central tracking systemAuthor: Alexander Borissov1

1 Wayne State University


Measurement of neutral meson production from photon decays at ALICE experiment is performedby means of two electromagnetic calorimeters (EMCAL and PHOS) and/or conversion of photons incentral tracking system. For two and more photon decaying mesons (pi^0, eta,omega)a possibility of combined calorimetry and conversion measurement is explored. It allows an inde-pendent cross check of data and systematic uncertainties given by two general approaches. pi^0spectrum from proton-proton collisions at sqrt(s) = 7 TeV is presented from the analysis of 2010 datawhere one photon detected inEMCAL and another from its conversion. Spectrum is compared withseparate measurement in each calorimeter. Perspectives of the applicability of combinedcalorimetry and conversion measurement are shown for 2011 data and PbPbcollisions.

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Low pT direct photon production in 200GeV d+Au collisions mea-sured by the PHENIX detector

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Author: Yorito Yamaguchi1



Direct photons in low pT region have been of great interest for a long time since thermal photonsfrom Quark Gluon Plasma (QGP) are considered to contribute predominantly.Attempts to measure low pT direct photons using EMCals could not succeed since a finite energyresolution of the EMCal prevents us from separating direct photon signal from a large amount ofbackground of hadron decay photons, particularly pi0.

Recently, the PHENIX experiment demonstrated that direct photon yield can be obtained even in lowpT region via the di-electron measurement since direct photon internal conversions make enhancedyield of di-electrons over the known hadron decay contributions.Comparing direct photon yields in√

sNN = 200GeV p+p and Au+Au collisions, a significant excessover the binary scaled p+p result is seen in Au+Au for pT<3GeV/c.

However, it should be confirmed that the observed excess of direct photons is not due to nucleareffects such as Cronin effect, nuclear anti-shadowing and so on, since nuclear effects are involved inAu+Au collisions but not in p+p collisions.d+Au collision data can contribute to quantify nuclear effects on direct photon production.The latest results of low pT direct photons from d+Au data taken in the Year-2008 RHIC Run will beshown.

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Studies for an upgrade of the ALICE Inner Tracking SystemAuthor: Cristina Terrevoli1

1 Universita degli Studi di Bari-Universita & INFN, Bari for ALICE ITS Collaboration


Heavy quarks are fundamental probes to investigate the properties of the hot and dense QCDmatterformed at the extreme energy densities reached in Pb-Pb collisions at LHC. The heavy quark pairs(cc_barand bb_bar), which are produced in the very initial stage of the collision, come out from the interac-tionregion as hadrons, possibly as a part of a jet, and carry out information about the properties of thetraversed medium. Such information can be obtained from the study of the open charm and beautyhadrons in the final state and of the associated jet. Charm and beauty hadrons decay weakly with ameanfree path of the order of few hundred microns. Therefore, their identification relies on the possibilityofresolving a decay vertex at distances of such order from the production one. The inner tracker ofthe ALICEexperiment (ITS), made of six layers of silicon detectors, has been designed and built to this purposeand isproviding the first results on the above mentioned item, though with some limitations. A detectorbased ontoday’s frontier technologies would certainly offer new exciting possibilities within the physicsscopedescribed above.This contribution will present the studies on the upgrade of the ALICE ITS detector. At the moment,severalpossible scenarios for the new detector layout and technologies are being considered. With respectto thecurrent ITS, the baseline idea for the upgraded tracker is to have a detection layer closer to the beamline

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(which implies a beam pipe with smaller radius) and a larger number of layers instrumented withsiliconpixels. The track position resolution at the primary vertex could be improved by a factor 2–3.Besides the natural improvement of the measurement capabilities on the channels already well mea-suredwith the present ITS, the upgraded ITS will offer the possibility of exploring new physics items. Ex-amples arethe heavy flavor baryons, the exclusive decay channels of B-mesons, the production mechanisms ofhadrons containing more than one heavy quark.

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Feasibility study of muon chamber for CBM experiment at FAIR

Author: Arun Prakash1

Co-authors: Anna Kiseleva 2; Bhartendu Kumar Singh 1; Evgeny Kryshen 3; Partha Pratim Bhaduri 4; SubhasisChattopadhyay 5

1 BHU,Varanasi,India2 GSI, Darmstadt, Germany3 SPbSPU, St Petersburg, Russia4 Variable Energy Cyclotron Centre, Kolkata,India5 Variable Energy Cyclotron Centre, Kolkata, India


The compressed baryonic matter (CBM) experiment at the future FAIR accelerator center in Darm-stadt, Germany, aims at the investigation of baryonic matter at highest net baryon densities butmoderate temperatures, by colliding heavy-ions at beam energies from 10 to 45 A GeV. The researchprogram comprises the exploration of basic landmarks of the QCD phase diagram like transitionsfrom hadronic to partonic phase, the region of first order de-confinement as well as chiral phasetransition, and the critical end point. The proposed key observables include the measurement of lowmass vector mesons and charmonia, which can be detected via their decay into the di-lepton chan-nel. As the leptons leave the hot and dense fireball without further interactions, hence they providealmost unscathed information about the interior of the collision zone where they are being created.In this paper, we discuss the physics motivation, detector concepts, and the feasibility studies ofthe di-muon measurements for central Au + Au collisions, with a special reference to the detailedsimulation activities performed by the CBM muon group.

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D meson production cross sections in pp collisions at √s = 7 TeV,measured with the ALICE detectorAuthor: Grelli Alessandro1

1 Utrecht University


Heavy quark production provides a powerful tool to test pQCD calculations in hadron collisionsin the new energy regime of the LHC. Moreover the D meson pt-differential cross section in ppcollisions provides the reference for the study of nuclear matter effects on charm quarks in PbPbcollisions, via the nuclear modification factor.

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The ALICE experiment collected data in pp collisions at √s of 7 TeV and 2.76 TeV at the LHC. Wepresent preliminary results on the pt-differential cross sections of D0, D*+, and D+ mesons, recon-structed using their hadronic decay channels. We show that already with a subsample of the 2010data, thanks to excellent tracking system and particle identification capabilities of the ALICE exper-iment, the charmed hadron measurements in the mid-rapidity region can be extended down to pT~2GeV/c, with good prospects to reach pT~1 GeV/c or below using the full sample. The current statusof the Ds and Λc analysis, as well as the investigation of the charm content in jets, are discussed aswell.

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Lattice study of the second order transport coefficientsAuthor: Yasuhiro Kohno1

Co-authors: Chiho Nonaka 2; Masakiyo Kitazawa 1; Masayuki Asakawa 1

1 Osaka University2 Nagoya University


We attempt to constrain transport coefficients in second order viscous hydrodynamics by SU(3) lat-tice gauge simulation for the range of temperature 0.5 < T/T_c < 4. On the basis of the relaxationtime approximation and Kubo formula, we relate a ratio of the shear viscosity to the relaxation timeof the shear stress to fluctuations of off-diagonal components of energy-momentum tensor on thelattice and evaluate them.

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Study of pion-pion correlations at LHC and RHIC energies in ppcollisions within the quark-gluon string modelAuthor: Mads Stormo Nilsson1

Co-authors: Evgeny Zabrodin 1; Larissa Bravina 1; Ludmila Malinina 2

1 Department of Physics, University of Oslo2 Skobeltzyn Institute for Nuclear Physics, Moscow State University, Moscow, Russia


The microscopic string model is employed for the description offemtoscopic characteristics of identical pions produced in ppcollisions at energies of sqrts = 200GeV (RHIC) andsqrts = 900GeV (LHC). The strong decrease of thecorrelation radius with increasing transverse momentum of the pionpair is found in accord to STAR and ALICE experimental observationswith flat baselines. In contrast to standard fit of the pioncorrelation function to single Gaussian, the double Gaussian fitreveals the contributions coming from resonances and from directlyproduced particles. The comparison of model results with theexperimental data favors decrease of particle formation time withrising collision energy. The model is also employed to calculate the three-dimensional correlationfunctions, which gives good agreement with ALICE experimental data.

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A comprehensive study of the high-pt particle correlations in ppcollisions at LHC/ALICEAuthor: Yaxian Mao1

1 CCNU, Wuhan & LPSC, Grenoble


Two-particle correlationwith the high-pT triggers allows the study of the hard scattering phenomenalike soft QCD radiation [1, 2], angular ordering [3] or jet fragmentation in the low and intermediatepT region [4, 5] where full jet reconstruction is challenging. An analysis of the first ALICE ppdata where charged particle, π0 and isolated photon are used as trigger particles will be presented.These measurements will serve as a reference for the same measurements in Pb-Pb collisions. Asensitivity of the associated particle momentum projection into the direction of the trigger particle,xE = −p Th± · p Ttrig / | p Ttrig |2, can be used to extract the average trigger particle momentumfraction and the jet imbalance function, whereas the γ-hadron correlations can be used to study thejet fragmentation function directly. The quest for the nuclear modification of the partonic propertiesin heavy ion collisions, using above mentioned quantities, will be also outlined.

References[1] D. Boer and W. Vogelsang, Phys. Rev. D69, 094025 (2004), hep-ph/0312320. [2] R. Perez-Ramos,F. Arleo, and B. Machet, Phys. Rev. D78, 014019 (2008), 0712.2212. [3] Y. L. Dokshitzer, D. Diakonov,and S. Troian, Phys.Rept. 58, 269 (1980). [4] PHENIX, S. S. Adler et al., Phys. Rev. D74, 072002 (2006),hep-ex/0605039.[5] PHENIX Collaboration, A. Adare et al., Phys. Rev. D 82, 072001 (2010), arXiv:1006.1347.

Heavy Flavors / 488

Charmoniumand open-charmproduction in p-A collisions at theSPSAuthor: Pietro Cortese1

1 Univ. del Piemonte Orientale, Dip.Scienze eTecnologie


p-A collisions provide an essential reference for the study of J/psi suppression in heavy-ion data sincethey allow to evaluate cold nuclear matter effects. These include initial state effects like shadowingand parton energy loss and final state effects like J/psi breakup in the collisions with cold nuclearmatter.

To evaluate these, NA60 has measured J/psi production in p-A collisions at SPS energies with sevennuclear targets. In this analysis the J/psi cross section has been compared with open-charm pro-duction that is detected in the NA60 experiment through the simultaneous semi-muonic decay ofD meson pairs. The comparison of the production of closed-charm with its natural reference al-lows to have some insight on how the interplay of the different processes gives rise to the observed(effective) J/psi suppression.

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Measurement of Low Mass Electron-Positron Pairs with ALICE

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Author: Christoph Baumann1

Co-author: Markus Köhler 2

1 IKF, Goethe-Universität Frankfurt2 EMMI, GSI

The ALICE experiment at the CERN-LHC is dedicated to study the properties of the Quark-GluonPlasma created in ultrarelativistic heavy-ion collisions. Low-mass electron-positron pairs arean excellent probe for all stages of the collision because they do not undergo strong final state in-teractions. With its unique tracking and particle identification capabilites extending to very lowmomenta, ALICE is excellently suited for these measurements. We will present first results on theproduction of low-mass electron-positron pairs at mid-rapidity in pp collisions at sqrt(s) = 7 TeVmeasured in ALICE and give an outlook on the low-mass program for Pb-Pb data.

490

Dissipative effect on the thermal photon spectraAuthor: Sukanya Mitra1

Co-authors: Jane Alam 1; Sourav Sarkar 1; payal mohnaty 1



The effects of the shear and the bulk viscositieson the transverse momentum distribution of thermal photonshave been studied. The effects of viscosity havebeen taken into account both in the phase spacedistributions of the particles taking part in theproduction process as well as in the space timeevolution. We argue that the thermal photons can beused as an efficient tool to estimate the transportcoefficients of quark gluon plasma.

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Femtoscopy of the proton-proton collisions at the LHCwith pion-pion Bose-Einstein correlations in ALICEAuthor: Adam Kisiel1

1 CERN


We report on the results of identical pion femtoscopy of the pp collisions at the LHC with the Bose-Einstein correlations. We present the final analysis of the ALICE pp datasets at sqrts= 0.9 TeV and7 TeV and the preliminary results for sqrts=2.76 TeV.

Detailed pion femtoscopy studies in heavy-ion collisions have shownthat emission region sizes (”HBT radii”) decrease with increasing pair momentum, which is under-stood as a manifestation of the collective behavior of matter. 3D radii were also found to universallyscale with event multiplicity. In pp collisions at sqers = 7 and 2.76 TeV one measures multiplicities

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which are comparable with those registered in peripheral Au-Au and Cu-Cu collisions at RHIC, sodirect comparisons and tests of scaling laws are now possible.

We show the results of double-differential 3D pion Bose-Einsteinfemtoscopic analysis, as a function of multiplicity and pairmomentum. The results for three collision energies are compared toresults obtained in the heavy-ion collisions at similar multiplicityand pp collisions at lower energy. We identify the relevant scalingvariables for the femtoscopic radii and discuss the similarities anddifferences to results from heavy-ions. The observed trends giveinsight into the soft particle production mechanism in pp collisionsand suggest that a self-interacting collective system may be createdin sufficiently high multiplicity events.


Resonance measurement in pp and PbPb collisions at LHC withthe ALICE detectorAuthor: Alberto Pulvirenti1

Co-author: – ALICE Collaboration 2

1 University / INFN Catania2 –


The study of resonances production in pp collisions contributes to the proper tuning of the QCD-inspired particle production models and to the better understanding of the underlying event, whilein PbPb collisions resonances are good probes to estimate the collective properties of the fireball,and in particular its lifetime.Strange resonances can also contribute to the historical topic of strangeness production measure-ment.pT spectra have been measured for φ, K ∗ , Σ∗ and Ξ∗ resonances using data from pp collisions at 7TeV in LHC, measured by the ALICE detector.Mesons were analyzed in a rapidity window of ±0.5 while baryons in a window of ±0.8. Results willbe shown from comparisons with several MC models, which show in general an acceptable match,except for the Ξ∗ which appear to be underestimated.Moreover, first results from the analysis of φ resonance in Pb-Pb collisions at 2.76 ATeV will bepresented.


K0sK0s correlations in 7 TeV proton+proton collisions from theALICE experiment at the LHCAuthor: Thomas Humanic1

1 Relativistic Heavy Ion Group, Department of Physics - Ohio State U.


Identical neutral kaon pair correlations are measured in 7 TeV proton+proton collisions in the AL-ICE experiment. Neutral kaons are identified from their decay into π+π- pairs. K0sK0s correlationfunctions are formed in 4 multiplicity x 4 kT bins. The kaon source parameters Rinv and λ are ex-tracted from these correlation functions by fitting a Gaussian*PYTHIA model to them, the Gaussian

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describing the Bose effect and PYTHIA accounting for the non-flat baseline found in proton+protoncollisions. PYTHIA with the Perugia-0 tune is seen to describe well the dependence of the baselineshape of the K0sK0s correlation function on multiplicity-kT bin in the Qinv fitting range used of 0-1GeV. Corrections to source parameters from the Lednicky model for the a0/f0 resonance are madeand found to be large. K0sK0s correlations show a systematic increase in Rinv for increasing multi-plicity bin and decreasing Rinv for increasing kT bin as seen in ππ correlations in the proton+protonsystem, as well as seen in heavy-ion collisions. Also, K0sK0s correlations are observed to more orless “smoothly” extend this ππ Rinv behavior for the proton+proton system to ~3 times higher kTthan the kT range measured in ππ correlations.

Jets / 495

Jet Reconstruction and Jet Background Classification with theALICE experiment in PbPb collisions at the LHCAuthor: Christian Klein-Boesing1

1 IKP Muenster


The quantification of the effect of parton energy loss, known as jetquenching, is one of the major goals of jet and high pTmeasurements in heavy-ion collisions. Here, the aim of the reconstruction ofjets, as compared to single particle measurements, is to provide a more directaccess to the original parton properties and the modification of thefragmentation process in heavy-ion collisions.

For a clear interpretation of the reconstructed jet properties and themeasurement of the inclusive jet spectrum in heavy-ion collisions a detailed characterization of thebackground and its fluctuation is paramount. In particular collectiveeffects within one event can enhance or deplete locally the level ofbackground and modify the jet energy scale.

The ALICE detector with its excellent tracking capabilities is theideal tool to study jet reconstruction based on charged particles in the presence ofcorrelated and uncorrelated background down to particle pT of 150MeV/c.

We will evaluate the evolution of background effects using differentprobes embedded into heavy-ion data and quantify their influence onthe reconstructed jet spectrum.

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Nuclearmodification of charmquarks inPb-Pb collisions at√sNN=2.76TeV at LHCAuthor: Umme Jamil1

Co-author: Dinesh Srivastava 2

1 SINP, Kolkata, India2 VECC, Kolkata, India


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The charm quarks are expected to be produced at theinitial fusion of the ultrarelativisticheavy-ion collisions. Just after the production, they will propagatethrough the Quark Gluon Plasma (QGP) and will loose energy bycolliding with quarks and gluons and radiating gluons.

We calculate the nuclear modificationfactor RAA of charmquarks, produced from the initial fusion of partonsin a nuclear collision, at √sNN=2.76 TeV Pb-Pb collision at LHC at more forward rapidities .

At therelativisticheavy-ion collisions, nuclear shadowing effect will also play an important role. In this study, wetake in to accountthe effect of collisional and radiative energy loss of the charmquarkswhile passing through the QGP and also the gluon shadowing effect while calculating RAA.

We have considered some of the importantformalisms available in the literature for the calculation of medium-induced radiative and collisionalenergy loss. The shadowing effect is introduced by using EKS 98parameterization for structure functions.


K0s and Lambda production in PbPb collisions with the ALICEexperimentAuthor: Iouri BELIKOV1

1 IPHC, CNRS-IN2P3


We present the study of K0s and Lambda production performed withthe ALICE experiment at the LHC in Pb-Pb collisions at sqrt(sNN)=2.76 TeV and pp collisions atsqrt(s)=0.9 and 7 TeV.The K0s and Lambda particles are reconstructed via their V0 decaytopology allowing their identification up to high transverse momenta.The corresponding baryon/meson ratios as a function of transverse momentum are extracted forPb-Pb collisions in centrality bins andin the transverse momentum range from 1 to 10 GeV/c.They are also compared with the ones measured in pp events at the LHC energies of 0.9 and 7 TeVas well as in Au-Au collisions at sqrt(sNN)=0.2 TeV from RHIC.

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Unintegrated gluondistributions andk_t-factorization in forwardhadron production in DIS and pA collisionsAuthor: Fabio Dominguez1


Two different forms of unintegrated gluon distributions have been widely used in the literature todescribe small-x phenomena. On one hand, the Weizsacker-Williams distribution explicitly counts

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the number of gluons per state in a physical gauge but does not seem to be related to any knownobservables. On the other hand, the unintegrated gluon distribution defined as the Fourier transformof the color dipole cross section appears naturally in gluon production cross sections but has nopartonic interpretation. We show that the Weizsacker-Williams distribution can be probed in a dijetproduction process in DIS whereas the Fourier transform of the color dipole appears in photon-jet production in pA collisions. More complicated processes involving two particle production canbe described with an effective k_t-factorization where each specific process requires a new gluondistribution built from the two basic ones through convolution.


Multi-strange particlemeasurements in 7 TeV proton-proton and2.76 TeV PbPb collisions with the ALICE experiment at the LHC

Author: D.D. Chinellato1

1 Instituto de Fisica Gleb Wataghin (IFGW) - Universidade Estadual de Campinas


Theproduction of chargedmulti-strange particles is studied with the ALICE experiment at the CERNLHC.Measurements of the central rapidity yields ofΞ− andΩ− baryons, aswell as their antiparticles,are presented as a function of transverse momentum (pT ) for inelastic pp collisions at

√s = 7 TeV

and compared to existing measurements performed at the same and/or at lower energies. The resultsare also compared to predictions from PHOJET and several tunes of the PYTHIA event generators.We find that data significantly exceed the production rates from those models, everywhere exceptpotentially for high pT , where hard QCD processes dominate. Finally, we present the status of themulti-strange particle production studies in Pb-Pb at

√s = 2.76 TeV performed as a function of

collision centrality.


The next decade of physics with PHENIXAuthor: Anne Sickles1

1 Brookhaven


The first decade of RHIC physics and the first heavy ion running at the LHC have produced a wealthof data and discoveries. It is timely to now evaluate what has been learned and ask what compellingnew questions have been raised. In this talk, several key unanswered questions about the propertiesof the strongly coupled quark gluon plasma and the distribution of partons inside nucleons and nucleiwill be discussed along with how they can be addressed experimentally. The PHENIX Collaborationhas developed a plan for upgrading the experiment in order to address these new questions. Thecurrent status of these plans will be presented.


Elliptic flow at high transverse momentum in PbPb collisions at√sNN = 2.76~TeV with the ALICE experiment

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Author: Alexandru Florin Dobrin1



As a consequence of the energy loss of highly energetic parton propagating through a dense medium,jet quenching is an important probe of QGP created in high energy heavy-ion collisions. Jet quench-ing leads to the suppression of particle production at high transverse momenta. An observable thatcan be used to better constrain the mechanism responsible for the parton energy loss is the ellipticazimuthal event anisotropy, v2, which provides differential information on the particle yield and jetquenching relative to the reaction plane.

We report on measurements of the elliptic event anisotropy for unidentified charged particles withpT up to 20~GeV/c in Pb-Pb collisions at √sNN = 2.76~TeV recorded by the ALICE experiment atthe LHC. Additionally, we report on measurement of v2 for identified particles with pT < 10~GeV/c;pions and protons are identified using the ionization energy loss in the TPC. The results are com-pared to the measurements at lower energy reported by RHIC experiments but also to theoreticalpredictions.

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Pt spectra of hadrons identified with the ALICE Inner TrackingSystemAuthor: Leonardo Milano1

1 Universita degli Studi di Torino-Universita e INFN


The Inner Tracking System is the ALICE detector closest to the beam axis. It is composed of sixlayers of silicon detectors: two innermost layers of Silicon Pixel Detectors (SPD), two intermediatelayers of Silicon Drift Detectors (SDD) and two outermost layers of Silicon Strip Detectors (SSD).The ITS can be used as a standalone tracker in order to recover tracks that are not reconstructed bythe Time Projection Chamber (TPC) and to reconstruct low momentum particles with pt down to100~MeV/c. Particle identification in the ITS is performed by measuring the energy loss signal inthe SDD and SSD layers. The ITS allows to extend the charged particle identification capability inthe ALICE central rapidity region at low pt: it is possible to separate π/K in the range 100 MeV/c< pt < 500 MeV/c andK/p in the range 200 MeV/c< pt < 800 MeV/c. The identification of hadronin the ITS will be discussed in detail, different methods used to extract the pt spectra of π,K and pwill also be described.

Heavy flavors / 503

Measurement of J/psi production at forward rapidity in pp colli-sions at sqrt(s)= 2.76 and 7 TeV with ALICEAuthor: Roberta Arnaldi1

1 INFN Torino


The ALICE experiment has studied J/psi production at forward rapidity from pT=0, through itsdimuon decay channel, in proton-proton and Pb-Pb collisions at the LHC.Results obtained in proton-proton collisions at sqrt(s)=7 TeV will be discussed. The integrated and

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differential (in pT and rapidity) inclusive production cross sections will be presented and comparedto results from other LHC experiments.First results on the J/psi integrated and differential cross sections in proton-proton collisions atsqrt(s)=2.76 TeV will also be discussed. These measurements, at the same centre-of-mass energyas for Pb-Pb collisions, provide a crucial reference for the study of nuclear matter effects on J/psiproduction.


Electrical conductivity and thermal dilepton rate from quenchedlattice QCD.Author: Olaf Kaczmarek1



We report on a continuum extrapolation of the vector current correlation function for light valencequarks in the deconfined phase of quenched QCD. This is achieved by performing a systematic anal-ysis of the influence of cut-off effects on light quark meson correlators at T=1.5 Tc using cloverimproved Wilson fermions [1]. In addition new results at 1.2 and 3.0 Tc will be presented.The first two, non-vanishing thermal moments of the vector meson spectral function are determinedand compared with those for free, massless quarks.We discuss resulting constraints on the electrical conductivity and the thermal dilepton rate in aquark gluon plasma.

[1] H.-T. Ding et al. Phys.Rev.D83(2011)034504


Measurement of π/K/p spectra with ALICE in proton-proton col-lisions at

√s = 900 GeV and

√s = 7 TeV

Author: Marek Chojnacki1

1 UU/NIKHEF


The ALICE experiment features several particleidentification systems, which allow us to measure spectra in a broad range of transverse momentumpt from 100 MeV/c up to a few GeV/c.New results on identified charged particle pt spectra measured in proton-proton collisions at

√s = 7

TeV will be presented.They will be compared to results obtained at 900 GeV and lower energies, theoretical models andcommonly used event generators.The large statistics collected in collisions at

√s = 7TeV allows us to measure the spectra and yields

as a function of the event multiplicity,reaching a dN/dη comparable to nuclear collisions at lower energy. The status and perspective ofsuch measurement will also be presented.


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Photons at RHIC and at the LHC: the role of viscosity and ofevent-by-event fluctuationsAuthor: Charles Gale1

Co-authors: Bjoern Schenke 2; Clint Young 1; Jean-Francois Paquet 1; Maxime Dion 1; Sangyong Jeon 1

1 McGill University2 Brookhaven National Laboratory


We investigate the yield and the azimuthal anisotropy of produced photons in heavy-ion collisionsat RHIC and at LHC energies. We study the photons produced from a variety of sources, includingthose from primordial nucleon-nucleon collisions, from thermal partons, from fragmenting QCDjets, from jets interacting with thermal partons, and from thermal hadrons. We study the interplayof those sources, in an evolving 3D simulation of the colliding system that involves hydrodynamicsand hard jets. We study ideal and viscous fluids, and we evaluate the effect of fluctuating initialconditions, and of using different hadronic equations of state. Under all of the above conditions,we quantify the ability of real photons to act as penetrating probes of the hot and dense stronglyinteracting medium.


Anisotropic flow of charged particles at 2.76 TeV measured withthe ALICE detectorAuthor: Ante Bilandzic1

1 NIKHEF


Ante Bilandzic for the ALICE collaboration

Measurements of anisotropic flow provided evidence for the creation of strongly interacting matterwhich appears to behave as an almost ideal fluid. Anisotropic flow signals the presence of multipleinteractions and is very sensitive to the initial spatial anisotropy of the overlap region in non-centralheavy-ion collisions. In this talk we report measurements of elliptic v2, triangular v3, quadrangularv4 and pentagonal v5 flow. These measurements have been performed with two- and multi-particlecorrelation techniques. We will show how these measurements can be understood from the initialspatial anisotropy and its fluctuations. These observations provide a possible explanation for theaway-side features often attributed to Mach cone effects.


Measurements of low mass dielectrons in Au+Au collisions withthe HBD upgrade of the PHENIX detectorAuthor: Mihael Makek1



Dileptons are valuable probes in the investigation of the hot anddense matter formed in heavy ion collisions, since they interact only electromagnetically and thus

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their path from the interaction region to the detectors is almost undisturbed. They can provideinformation about the matter properties in the early stages of the collisions where deconfinementand chiral symmetry restoration are expected to take place. However, themeasurements of dileptonsin heavy ion collisions are challenging due to the overwhelming yield of pi0 Dalitz decays and photonconversions, which produce a large combinatorial background especially in the low invariant massregion (m_ee<1 GeV/c^2).

The PHENIX spectrometer has been upgraded with a Hadron Blind Detector (HBD) with the pur-pose of reducing the combinatorial background from the dielectron mass spectrum. The HBD is awindowless Cherenkov detector, operating with pure CF_4, using triple GEM elements with a CsIphotocathode and pad readout. The HBD reduces the combinatorial background by exploiting thesmall opening angle of the pi0 Dalitz and conversion pairs. It was successfully operated during Run9 and Run 10 at RHIC in the measurements of e+e- pairs in p+p collisions at sqrt(s)=200 GeV andin Au+Au collisions at sqrt(s_NN) = 200 GeV, 62 GeV and 39 GeV. In this talk a full account of theHBD and present results of the dielectron analysis in Au+Au collisions at sqrt(s_NN)=200 GeV withimproved signal to background ratio, will be presented.

Heavy flavor / 509

Heavy-flavor production cross section in the semi-electronic chan-nel at mid-rapidity in pp collisions at sqrt(s)=7 TeV with ALICE

Author: Silvia Masciocchi1

1 GSI Darmstadt


Heavy quarks (charm and beauty) are among the most important probes that allow to test perturba-tive QCD descriptions of hard processes in hadronic interactions, as well as to study the hot matterproduced in high energy nucleus-nucleus collisions. Precision measurements of heavy flavour pro-duction in proton-proton collisions provide the necessary reference for the interpretation of theirbehaviour in the deconfined state of strongly-interacting matter (Quark-Gluon Plasma). Both colli-sion systems can be extensively studied with ALICE at LHC.

The production of heavy quarks can be measured via the detection of their semileptonic decays. Wepresent the measurement of the inclusive electron spectrum at mid-rapidity, in proton-proton colli-sions and sqrt(s)=7 TeV, based on the excellent particle identification capabilities of ALICE.

The statistical subtraction of a cocktail that accounts for photonic electrons and other backgroundsources, built on the base of ALICE measured meson spectra, provides a measurement of the pro-duction cross section of electrons from heavy-flavour hadron decays. The further subtraction of thecharm component, obtained from the D meson cross section measured by ALICE in the same rapid-ity range, as well as an analysis of impact parameter distributions relative to the interaction vertex,allow to determine the electron spectrum from pure beauty decays.

The results will be presented, compared to theoretical predictions, and discussed in the perspective ofobtaining a reference for the studies of heavy quark energy loss in theQuark-Gluon Plasma.

Energy scan / 510

Collision energy dependence of the flow and spectra results inAu+Au collisions at √sNN = 7.7-200 GeV from PHENIX

Author: Xiaoyang Gong1

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A central goal in experimental nuclear physics is to map out the QCD phase diagram, and to measureprecisely the properties of the different phases. In order to achieve this goal, RHIC has embarked onan energy scan program involving gold nuclei at various energies. The data collected by the PHENIXexperiment for this program consists of data sets obtained at√sNN = 200, 62, 39 and 7.7 GeV.

The analysis of these data, have yielded a wealth of new soft physics results which are used in con-cert to probe reaction dynamics and to constrain the transport coefficients of hot QCD matter. Oneparticularly effective probe that is emphasized in this talk is the anisotropy of particle production,characterized by flow coefficients v2 and v4. For Au+Au collisions at √sNN = 200 GeV, measure-ments indicate a hydrodynamic flow of hot QCD matter at the partonic level with a small but finitevalue of the viscosity to entropy density ratio. However, at sufficiently low collision energy (thuslower energy density and temperature), we expect this picture to break down. Therefore measure-ment of the collision energy dependence of v2 and v4 could provide new insights to the currentunderstanding of the nature of interactions in hot QCD matter.

We present new energy scan measurements of flow coefficients for both unidentified and identifiedparticles, as well as several other soft physics observables such as identified hadron spectra and HBTcorrelations. The implications of these results will also be discussed.

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Newexperiments for study of in-mediumvectormesons at J-PARC

Author: Kyoichiro Ozawa1

1 KEK

The origin of the hadron mass has been drawing strong interests in nuclear and particle physics.Especially in QCD, mass of hadrons is composed of a sum of the effective mass of valence quarks,known as constituent quark mass, and their interaction term. According to theoretical models, theeffective mass of valence quarks is determined by chiral property of QCD vacuum. This mechanismis understood as a consequence of the dynamical breaking of chiral symmetry. In hot and/or densematter, this broken symmetry will be restored either partially or completely and, hence, propertiesof hadrons, such as mass, decay modes and life time, can be modified. Therefore, we can study theorigin of hadron mass and chiral properties of QCD medium by measuring in-medium propertiesof mesons. Especially, mass spectra of vector mesons are directly connected to anti-quark quarkcondensates, which is an order parameter of chiral symmetry. Thus, it is important to measure massspectra of vector mesons in QCD medium, such as Quark Gluon Plasma or nuclear matter.Even at nuclear matter density, relatively large mass modification is predicted and several experi-mental efforts using cold nucleus targets are already performed. Among these activities, KEK-E325reported significant mass modifications for rho and phi mesons and CLAS G7 experiment reportonly mass broadening for rho meson. Obtained results are different and physics behind these exper-imental results are not clearly understood.To understand the physics, clear and high statistics experimental data are essential. We are prepar-ing new experiments to obtain such data at J-PARC. One experiment is an upgrade of E325 and aimsto collect 100 times larger statistics in phi going to e+e- decays. Another experiment focus on exclu-sive measurements of stopped omega meson in nucleus.In this poster, we will report on details of two experiments and results of detector R&D.

Energy scan / 512

Energy dependence of energy loss inAu+Au collisions at PHENIX

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Author: Norbert Novitzky1

1 Department of Physics-University of Jyvaskyla


The suppression of inclusive pion production by up to a factor of 5, which was first observed in Au+ Au at √sNN= 130 GeV/c (e.g. [1]) and later in Au + Au at √sNN= 200 GeV/c [2, 3], is one of themost significant manifestations of the opaque QGP produced in heavy ion collisions. The absenceof this suppression in d + Au collisions at the same energy indicates the final state nature of thesuppression. It is natural to ask where the onset of such massive suppression is in terms of theenergy density of the medium which is dictated by the collision energy, centrality and the massof colliding nuclei. The PHENIX collaboration has studied collisions of lighter nuclei (Cu + Cu) atdifferent beam energies in 2005 [4]. While a significant suppression is observed both at √sNN = 200and 62.4 GeV, at √sNN = 22.4 GeV a moderate enhancement is found. In 2010 RHIC scanned lowerenergies, and PHENIX collected substantial data sets in Au + Au collisions at √sNN = 39 and 62 GeV.The goal was to identify better the conditions for the onset of the π0 suppression. This talk presentsresults from the systematic study of c.m. energy and the system size dependencies of π0 yield andthe nuclear modification factor.References[1] K. Adcox et al., Phys.Rev.Lett. 88, 022301 (2002).[2] S. S. Adler et al., Phys.Rev.Lett. 96, 202301 (2006).[3] A. Adare et al., Phys.Rev.Lett. 101, 232301 (2008).[4] A. Adare et al., Phys.Rev.Lett. 101, 162301 (2008).

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Pseudorapidity density of charged particles and its centrality de-pendence in Pb-Pb collisions at √sNN = 2.76 TeV

Author: Hans Hjersing Dalsgaard1

1 Niels Bohr Institute, University of Copenhagen


Hans Hjersing Dalsgaard\footnote\[email protected]\\(for the ALICE collaboration)

We present the first measurements of the pseudorapidity (η) distribution in a wide range for differentcentralities in Pb-Pb collisions at √sNN = 2.76 TeV. Using the SPD and FMD detectors of ALICEwe can cover a wide region in η: −3.4 < η < 5. The distributions yield the total number ofproduced charged particles in Pb+Pb collisions at the LHC energy. Thedependence of dNch/dη on the number of participant nucleons oron the number of binary collisions is sensitive to models describing the mechanism underlying par-ticle production (eg. gluonsaturation models). In this contribution ALICE data will be compared to current models and ananalysis of longitudinal scaling will be performed.

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System-size dependence of particle ratio fluctuations in Pb+Pbcollisions at 158 AGeVAuthor: Dmytro Kresan1

1 GSI, Germany

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According to theQCD calculations on the lattice, the dynamical fluctuations of, for example, strangenessto entropy ratio could be enhanced in the co-existance region of the first order phase transition fromhadronic to partonic degrees of freedom and in the vicinity of the critical point.The energy dependence of the K/pi ratio fluctuations measured by theNA49 experiment in central Pb+Pb collisions shows increase towardslower energies, which is not reproduced by the UrQMD model. One ofthe possible explanations is the scaling of the dynamical fluctuations with average kaon multiplicity.In order to study this hypothesis one would like to fix the acceptance of the detector and measurethe event-by-event fluctuations as a function of centrality at fixed beam energy.In this poster, the centrality dependence of event-by-event fluctuations of K/pi, p/pi and K/p ratiosmeasured by the NA49 experiment in Pb+Pb collisions at 158A GeV will be presented. For all consid-ered ratios, dynamical fluctuations are found to increase in absolute value by 7 - 10% with decreasingcentrality. Comparing the centrality and energy dependence of the particle ratio fluctuations, theyare found to scale with the particle number dominating the fluctuation measure. I.e. in particular theevent-by-event K/pi fluctuations are found to scale with the number of kaons. For p/pi fluctuationsthe observed scaling supports the interpretation that the measured dynamical fluctuations are a rem-nant of nucleon resonance feeddown. Detailed investigations have been performed to systematicallystudy the influence of detector acceptance and particle identification.

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LHC results on femtoscopic pi+pi correlations from the UrQMDtransport approachAuthor: Gunnar Gräf1




We use the non-equilibrium transport approach Ultra-relativistic Quantum Molecular Dynamics(UrQMD) [1] to compute the dynamics of heavy ion collisions up to LHC energies. From this modelwe obtain directly the full phasespace distribution of all particles at the kinetic freeze out. By usingthe quantum reweighting technique on the freeze out distribution we extract the two-particle corre-lation function in three-dimensions. Using a gaussian parametrization we get the Hanbury-BrownTwiss (HBT) radii from these correlation functions which can be interpreted in terms of the space-time extension [2] of the particle-emitting source. A comparison of correlation functions and HBTradii with LHC data will be shown.

[1] S. A. Bass et al., Prog. Part. Nucl. Phys. 41 (1998) 225.

[2] S. Chapman et al., Phys. Rev. Lett. 74 (1995) 4400


Validity of the hadronic freeze-out curveAuthors: Francesco Becattini1; Marcus Bleicher2; Michael Mitrovski3; Reinhard Stock4; Thorsten Kollegger2; TimSchuster4

1 Universita de Firenze and INFN Sezione di Firenze2 rankfurt Institute for Advanced Studies (FIAS)3 Brookhaven National Laboratory, Physics Department

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4 Institut fuer Kernphysik - Johann-Wolfgang-Goethe Univ.


In nucleus-nucleus collisions we distinguish early hadro-chemical freeze-out, fixing hadronic con-centrations, and final kinetic freeze-out to spectral and flow features, occuring at the end of thehadronic “cascade” phase. This view has been adopted in all recent analysis of hadron productionrates, which are well described in the grand canonical statistical equilibrium model. The derivedfreeze-out systematics in the (T,mu(B)) plane occurs in all present sketches of the QCDmatter phasediagram. It merges with the lattice QCD parton-hadron coexistence line at small mu(B).

The preservation of the equilibrium pattern of hadronic yields (established in the close vicinity ofhadronization) throughout the final hadronic expansion phase still remains to be explained, and sub-stantiated.In order to systematically assess the effect of the hadronic cascade stage we employ the hybrid ver-sion of the UrQMD transport model. In it, a high density hydrodynamic evolution stage is matched,via the Cooper-Frye formalism, to the final hadron/resonance expansion evolution. Matching occursat a fixed critical energy density. These calculations are carried out at the energies covered by theSPS Pb+Pb program, 6.3 < squrr(s) < 17.3 GeV. At each energy we determine, both, the hadronyield distribution arising directly after hadronization, and the eventual distribution resulting fromthe UrQMD hadron/resonance expansion “afterburner” stage. The latter turns out to preserve thebulk production channels but to systematically reduce the antibaryon yields, with exception of theOmega/Antiomega. We revisit the data in view of these predictions.

Finally we analyze all these yield distributions with the grand canonical statistical model, determin-ing the freeze-out curve before/after the cascade afterburner. A significant shift of this curve occurs(to lower T, higher mu(B)) which, however, is essentially absent if the antibaryon yields are excluded,but with exception of the Omega/antiOmega yields. The cascade stage thus appears to distort theinitially imprinted equilibrium distributions, but only selectively so: an effect that must be avoidedin the data analysis. Thus one recovers the T, mu(B) established before the cascade stage.

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Derivation of Causal Relativistic Hydrodynamic Equations andNovel Moment MethodAuthor: Kyosuke Tsumura1

Co-author: Teiji Kunihiro 2

1 Fuji Film Co.2 Kyoto University


This is an extention of our previous work[1,2] to the derivation of the causal relativistic hydro-dynamic equations in generic local rest frames for a viscous fluid from the relativistic Boltzmannequation. Our derivation is based on the renormalization group method[3] as a powerful reductiontheory of the dynamics. We have identified some drawbacks in our previous derivationof the casusal equations[4]. Our improved equation is a natural extension of the first-order equationderived by the present authors.[1] The relaxation times derived in our microscopic theoryhave forms which can be nicely interpreted in terms of correlation functions. Our equation in anylocal rest frame including the particle frame has a definite stable thermal equilibrium state andis completely free from the instability problem.Our equation in the energy-frame is found quite different from the one by Denicol et al [5] which isderived on the basis of a moment method; but our equation can be well approximatedby it when the Rits approximatin is valid for a rarefied gas. On the basis of our derivation, we pro-pose the correct moment method for the derivation of causal hydrodynamic equations withoutad-hoc ansatz.

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References[1] K. Tsumura, T. Kunihiro and K. Ohnishi, Phys. Lett. B 646 (2007) 134.[2] K.Tsumura and T. Kunihiro, Phys. Lett. B 668 (2008) 425.[3] L.Y.Chen, N.Goldenfeld and Y.Oono, Phys. Rev. Lett.73 (1994) 1311;T.~Kunihiro, Prog. Theor. Phys.94 (1995) 503 [Erratum-ibid.95 (1996) 835].[4] K.Tsumura and T.Kunihiro, Phys. Lett. B 690 (2010) 255.[5] G.S.Denicol, T.Koide and D.H.Rischke, Phys. Rev. Lett. 105 (2010) 162501

Heavy Flavors / 519

Recent PHENIX results on open heavy flavorAuthor: J. Matthew Durham1


Throughout the history of the RHIC physics program, questions concerning the dynamics of heavyquarks have generated much experimental and theoretical investigation. A major focus of thePHENIX experiment is the measurement of these quarks through their semi-leptonic decay chan-nels at mid and forward rapidity.

Heavy quark measurements in p+p collisions give information on the production of heavy flavor,without complications from medium effects. New measurements in d+Au indicate significant andsurprising cold nuclear matter effects on these quarks at midrapidity, and provide a new baselinefor interpretation of the observed suppression in Au+Au collisions. To complement the measuredheavy quark spectra, correlations between heavy quark decay products give information on jet mod-ification in nuclear collisions, while correlations between heavy quarks and hadrons produced in thesame event can shed light on interactions with the medium. When considered all together, thesemeasurements present a detailed study of nuclear matter across a wide range of system size and tem-perature. This talk will present new PHENIX measurements of non-photonic electron spectra andtheir centrality dependence in d+Au, and discuss their implications on the current understanding ofparton energy loss in the nuclear medium.

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Triangular flow and nonflow by 2-, 4-, and 6-particle cumulantsfrom STARAuthor: Li Yi1

1 Purdue University


Triangular flow (v3) can arise from event-by-event fluctuations. Its connection to fluctuations in theinitial state collision geometry may reveal hydrodynamic information of the collision system.Theoretical studies suggest its sensitivity to hydrodynamic evolution may even be stronger than el-liptic flow (v2).We present v3 measurement by the 2-, 4-, and 6-particle cumulant method at √sNN = 200 GeV inAu+Au collisions by STAR.We compare our v3 results to v2, also from the multiparticle cumulant method.The 2-particle cumulant result contains nonflow contribution. We assess the nonflow effect by sep-arating charges as well as applying a pseudo-rapidity gap.The 4- and 6-particle v3 results are strongly affected (perhaps dominated) by v3 fluctuations.Assuming Gaussian flow fluctuation, we further attempt to distinguish flow, flow fluctuation, andnonflow.

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Midrapidity charged particle directed flow in PbPb collisions atsqrts_NN = 2.76 TeV measured with ALICE at the LHCAuthor: Ilya Selyuzhenkov1

1 EMMI/GSI


Azimuthal anisotropic flow is a key observable indicating collectivity among particles produced innon-central heavy ion collisions. Directed flow is characterized by the first harmonic coefficient inthe Fourier decomposition of the particle azimuthal distribution with respect to the collision reactionplane. It develops at a very early stage of the collision and thus is sensitive to the properties and theequation of state of the hot and dense matter produced in ion-ion collisions.

We report on results for midrapidity (|eta|<0.8) charged particle directed flow measured in lead-leadcollisions at 2.76 TeV collision energy recorded with the ALICE detector at the LHC. The orienta-tion of the collision reaction plane is reconstructed with the help of the spectator neutrons detectedby the pair of ALICE Zero Degree Calorimeter detectors. Directed flow results obtained with dif-ferent measurement techniques are presented as a function of collision centrality, charged particletransverse momentum, and pseudo-rapidity.

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Photonuclear interactions in ultra-peripheral Pb+Pb collisions atthe LHCAuthors: Joakim Nystrand1; Oeystein Djuvsland1

1 Department of Physics & Technology-University of Bergen


The strong electromagnetic fields present in ultra-peripheral Pb+Pb collisions at the CERN LHCaccelerator lead to large cross sections for particle production in photonuclear interactions[1]. Itwill be shown that photonuclear processes may constitute a significant background to peripheraland semi-central hadronic nuclear collisions.

The cross sections for photonuclear interactions induced by photons from the electromagnetic fieldsof the nuclei have been calculated. The photon spectrum has been evaluated in impact parame-ter space. Thereby one can easily exclude collisions were the nuclei interact hadronically (b < 2R).For modelling the particle production, the DPMJET[2] Monte Carlo event generator has been used.Calculations have been done for photon energies from 6 GeV to 100 TeV in the rest frame of thetarget nucleus, which is the energy range contributing to particle production around mid-rapidity.The multiplicity, rapidity, and transverse momentum distributions of produced particles will be pre-sented.

Two cases of photonuclear processes have been considered, single and double excitation. In theformer case, one of the nuclei emits a photon which interacts with the other nucleus, whereas inthe latter case both nuclei emit photons which interact with the other nucleus. The cross sectionfor single excitation is much larger than that of double excitation. However, the topology of thedouble excitation events, where the rapidity distruction is more symmetrical, is simililar to thatof hadronic interactions. Both processes may thus contribute significantly to the background ofhadronic interactions, depending on the experimental event selection.

The photon-nucleon energies that can be reached in ultra-peripheral collisions at the LHC are higherthan for any earlier gamma+Aor gamma+p collisions. In addition to being a background for hadronic

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interactions, such events have a physics interest in themselves. Photoproduction of heavy quarks(e.g. cc-bar through gamma-gluon fusion) and jets have large cross sections and probe the nuclearparton distribution functions.

[1] O. Djuvsland, J. Nystrand, arXiv:1011.4908, to be published in Phys. Rev. C.

[2] S. Roesler, R. Engel, J. Ranft, Phys. Rev. D 57 (1998) 2889.


Event-by-event mean pT fluctuations in pp and PbPb collisionsmeasured by the ALICE experiment at the LHCAuthor: Stefan Heckel1

1 Johann-Wolfgang-Goethe Univ.


Non-statistical event-by-event fluctuations of the mean transverse momentum of charged particlesin pp and Pb–Pb collisions are studied using the ALICE experiment at the LHC. The analysis is per-formed at |η| < 0.8 and 0.15 < pT < 2~GeV/c. Multiplicity dependent results are obtained forpp collisions at

√s~=~0.9, 2.76 and 7~TeV. Pb–Pb collisions at √sNN~=~2.76~TeV are analysed in

intervals of multiplicity and centrality, the latter in bins of 5\%.Little collision energy dependence is observed in pp collisions. The data indicate a common scal-ing behaviour with event multiplicity from pp to semi-central Pb–Pb collisions. In central Pb–Pbcollisions, the results deviate from this trend, exhibiting a significant reduction of the fluctuationstrength. The results are compared to measurements in Au–Au collisions at lower collision energiesand to Monte Carlo simulations with PYTHIA and HIJING.

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Shear viscosity in a partonic cascadeAuthors: Christian Wesp1; Felix Reining1

1 Goethe Universität Frankfurt


We simulate an ultra-relativistic gluon gas in a partonic cascade using the Boltzmann Approach forMulti Parton Scattering (BAMPS) with pQCD-based interactions. Furthermore elastic 2<->2 and in-elastic 2<->3 processes with constant cross sections are implemented. The hydrodynamic transportparameter shear viscosity is extracted via two different approaches: first from a relativistic station-ary velocity gradient and in a second method from equilibrium fluctuations using a Green-Kuborelation. Both methods are compared to an analytic relation and are used to investigate the alpha_sdependece of the shear viscosity to entropy ratio in a partonic gas at T>T_c.

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My suppression, your flow, his Cronin - our insightAuthor: Gabor David1

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Despite rapidly improving experimental precision,theory sophistication and the large variety of available data a coherentdescription of the properties of the hot, dense medium produced inrelativistic heavy ion collisions remain so far elusive. Using SPS, RHICand LHC heavy ion nuclear modification and flow data we will look at theevolution (system size and collision energy) as well as the interplay ofinitial state effects, dynamic and static properties of the medium.We will look at the data in some unorthodox ways in order to clarifywhat we can and what we can not learn from these type of measurements.


PHENIXmeasurements of higher-orderflowharmonics inAu+Aucollisions at√sNN = 200GeV: implications for Initial-eccentricitymodels and the specific viscosity of theQuarkGluon PlasmaAuthor: Roy Lacey1



The higher-order flow harmonics vn can provide constraints crucial for precision extraction of thespecific shear viscosity eta/s, of the plasma (QGP) produced in full energy (√sNN = 200 GeV)Au+Au collisions at RHIC. It can also provide reliable estimates of the flow correlations which con-tribute to the underlying event for jet-driven two-particle azimuthal angle correlation studies; thelatter is important to the development of a quantitative understanding of the opacity of the QGP.Thus, significant recent attention has been given to theoretical studies of vn (odd and even) and theassociated initial [fluctuating] eccentricities which drive vn.In recent experiments, the PHENIX Collaboration has madedetailed differential measurements of vn (odd and even) relativeto the participant event planes Ψn, as well as measurements of the correlations between differentΨn planes. The results from these measurements will be presented. Comparisons to LHC data andhydrodynamical calculations will be shown as appropriate. We will also discuss the detailed im-plications of these measurements for (i) improved precision for separating the flow and jet-drivencontributions to ∆Φ correlation functions, (ii) distinguishing between the two leading eccentricitymodels, and (iii) a more constrained estimate of η/s.

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Charged-particle transversemomentumspectra in proton-protoncollisions at √s = 0.9 TeV, 2.76 TeV and 7 TeV measured with AL-ICE at the LHCAuthor: Michael Linus Knichel1

1 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm-stadt, Germany


Inclusive charged-particle transversemomentumdistributions have beenmeasured in proton-protoncollisions at √s = 0.9, 2.76 and 7 TeV with the ALICE detector at the LHC. The measurements in the

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central pseudorapidity region |η| < 0.8 cover a transverse momentum range of 0.15 < p_T < 50 GeV/c.The evolution of the transverse momentum spectra as a function of the collision energy and thecharged particle multiplicity is presented. The spectra are compared to measurements from otherexperiments, to predictions from next-to-leading order QCD calculations and to simulations withthe Monte Carlo event generators PYTHIA and PHOJET. The results can be used to tune theoreticalmodels and serve as the baseline for the comparison with particle production in heavy-ion colli-sions.

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Electromagnetic superconductivity of vacuum in strongmagneticfield and heavy ion collisionsAuthor: Maxim Chernodub1

1 University of Tours, France


Recently, we have suggested that the vacuum in a strong external magnetic field experiences a spon-taneous phase transition to an electromagnetically superconducting state. The unexpected supercon-ductivity of, basically, empty space is induced by emergence of quark-antiquark vector condensateswith quantum numbers of electrically charged rho mesons. The ultra-periferal heavy-ion collisionsgenerate high magnetic fields which may be used as an experimental tool to probe the existenceof the electromagnetic superconductivity of the cold vacuum. In our talk we discuss potentiallyobservable signatures of vacuum instability towards the exotic superconducting state.

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Measurement of theNuclearModification Factor of Electrons fromHeavy FlavourDecays atMid-Rapidity inPb-PbCollisions at sqrt(s_NN)=2.76TeV with ALICEAuthor: Yvonne Pachmayer1

1 Ruprecht-Karls-Universitaet Heidelberg-Unknown-Unknown


In high-energy nucleus-nucleus collisions, heavy flavour quarks, i. e. charm and bottom, are pro-duced on a very short time scale in the initial hard scattering processes and thus they experience thewhole history of the collision. Therefore, they are valuable probes to address the features of the in-teraction of hard partons with the hot and dense state of matter, that is expected to be formed in thecollision. In particular, they allow us to study parton energy loss and its quark mass dependence.Heavy flavour production can be measured in several channels by the ALICE experiment at theLHC. We present the transverse momentum spectrum of electrons from heavy flavour decays atmid-rapidity in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV, as obtained by subtracting from the inclu-sive electron sample a data-tuned cocktail of the non-heavy-flavour background contributions. Bycomparison with a pp reference scaled to the same centre-of-mass energy, we determine the nuclearmodification factor of the pt distribution of electrons from heavy flavour decays.

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Charmonium dynamics in the UrQMD transport model

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Author: Thomas Lang1




We study charmonium physics in heavy-ion collisions within the frameworkof the non-equilibrium transport model UrQMD.Using this model we compute different heavy quark observables like thenuclear modification factor RAA, high pT suppression and theelliptic flow v2.The UrQMD approach includes explicit interactions of the charmed particleswith the surrounding medium.Different cross sections for charmonium dissociation and charmoniumrecombination by D-Mesons are tested at SPS, RHIC and LHC energies.We show that these results are in good agreement with measurements at thedifferent collision energies.

Energy scan / 532

Net-baryon-, net-proton-, andnet-charged particle kurtosis in heavy-ion collisions within a relativistic transport approachAuthors: Marcus Bleicher1; Marlene Nahrgang2; Michael Mitrovski3; Reinhard Stock4; Tim Schuster4

1 Frankfurt Institute for Advanced Studies(FIAS)2 Goethe University Frankfurt and Frankfurt Institute for Advanced Studies (FIAS)3 Physics Dept.,BNL, Brookhaven4 Frankfurt Institute for Advanced Studies(FIAS) and Institut fuer Kernphysik, University of Frankfurt


We explore the potential of net-baryon, net-proton and net-chargekurtosis measurements to investigate the properties of hot and densematter created in relativistic heavy-ion collisions. Contrary tocalculations in a grand canonical ensemble we explicitly take intoaccount exact electric and baryon charge conservation on anevent-by-event basis. This drastically limits the width of baryonfluctuations.A simple model to account for this is to assume Poisson distributions with a sharp cut-off at the tails.We present baseline predictions of the energy dependence of thenet-baryon, net-proton and net-charge kurtosis for central (b ≤ 2.75~fm) Pb+Pb/Au+Au collisionsfrom Elab = 2A~GeV to√sNN = 200~GeV from the UrQMD model. While the net-charge

kurtosis is compatible with values around zero, the net-baryon number decreases to large negativevalues with decreasing beam energy. The net-proton kurtosis becomes only slightly negative for low√sNN .

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Photoproduction ofVectorMesons inUltra-Peripheral Pb-PbCol-lisions at the LHCAuthor: Joakim Nystrand1

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1 Department of Physics and Technology


The strong electromagnetic fields surrounding the Pb-ions accelerated at the CERN Large HadronCollider (LHC) allow two-photon and photonuclear interactions to be studied in a kinematic regimeso far unexplored. In ultra-peripheral collisions, with impact parameters larger than the sum ofthe nuclear radii, hadronic interactions are strongly suppressed but the cross sections for electro-magnetic or photon-induced interactions are large. The interactions can be purely electromagnetic(two-photon interaction) or a photon from the field of one of the nuclei may interact with the othernucleus (photonuclear interaction). Exclusive interactions, where both nuclei remain in their groundstate, are dominated by coherent photonuclear vector meson production and two-photon productionof di-lepton pairs.

During the heavy-ion run at the LHC in 2010 where Pb-Pb collisions at an energy of sqrt(s_NN) =2.76 TeV were studied, the ALICE Experiment had triggers enabled for exclusive particle productionin ultra-peripheral collisions. These included trigger information from the Time-of-Flight, SiliconPixel, and V0 Detectors. A trigger for ultra-peripheral collisions was also enabled in the muonarm. The integrated luminosity for the ultra-peripheral triggers corresponds to about 3.6 microb^-1. Results on photoproduction of rho0 and J/Psi from the data collected with these triggers will bepresented.

Coherent rho0 production at mid-rapidity at the LHC corresponds to a photon-nucleon center ofmass energy of 45 GeV, roughly a factor of 4 higher than has been studied before. Photoproductionof J/Psi is of particular interest, since it has been proposed as a sensitive probe of the nuclear gluondistribution down to x = 10^-3. The results can be compared with models with different mechanismsfor the nuclear shadowing.

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Measurement of J/ψ → e+e− Production in Pb-Pb Collisions at √s= 2.76 TeV with ALICE at the LHCAuthor: Julian Book1

Co-author: Jens Wiechula 2

1 Institut fuer Kernphysik - Frankfurt2 Eberhard-Karls-Universitaet Tuebingen


The investigation of the properties of strongly interacting matter under extreme conditions is theaim of the LHC heavy ion program. Quarkonia states such as the J/ψ will provide insights intothe earliest and hottest stages of heavy ion collisons where the formation of a Quark-Gluon Plasma(QGP) is expected.Measuring these bound states of heavy quarks via their dileptonic decay modes is one of the goalsof the ALICE experiment. We will present the current status of the challenging J/ψ analysis in theelectronic decay channel at √s = 2.76 TeV in Pb-Pb collisions. Invariant mass spectra as well asfirst estimates of J/ψ yields are obtained using the tracking and particle identification capabilitiesof the Inner Tracking System (ITS), the Time Projection Chamber (TPC) and the Time of Flight(TOF).

Heavy flavors / 535

J/psi production at forward rapidity inPbPb collisions at sqrt(s_NN)= 2.76 TeV, measured with the ALICE detector

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Author: Philippe Pillot1

1 SUBATECH, Nantes


Heavy quarkonium states are expected to provide essential information on the properties of thehigh-density strongly-interacting system formed in the early stages of high-energy heavy-ion col-lisions. Such probes are especially promising at LHC energies, where heavy quarks are copiouslyproduced.

ALICE is the experiment at the LHC mainly dedicated to the study of nucleus-nucleus collisions. Atforward rapidity (2.5 < y < 4), the production of heavy quarkonium states is measured down to pT =0 via their mu+mu- decay channels in the Forward Muon Spectrometer. After a short description ofthe apparatus, the analysis of the inclusive J/psi production in the first Pb-Pb data collected in thefall 2010 at a center of mass energy of sqrt(s_NN) = 2.76 TeV will be presented. Preliminary resultson the nuclear modification factor (R_AA) and the central to peripheral nuclear modification factor(R_CP) will then be discussed.


Lowmass dimuonproduction in proton-nucleus collisions at√s =

27.5~GeV with the NA60 experimentAuthor: Antonio Uras1

1 INFN Cagliari, IPNL Lyon


The study of the production of low mass vector and pseudoscalar mesons in proton-nucleus colli-sions represents a natural baseline for the heavy-ion observations, allowing to provide a reference inan environment of cold nuclear matter. In-medium modifications of the vector meson spectral func-tions were actually predicted to occur also in cold nuclear matter, though the experimental evidenceat the moment is controversial. Proton-nucleus collisions also give access to the study of strangenessproduction as a function of the size of the nucleus, providing a robust ground for strangeness en-hancement in nuclear collisions. Besides that, the study of the nuclear dependence of particle prop-erties in proton-nucleus collisions, as the transverse momentum spectra and the production crosssections, is an effective tool to understand the dynamics of soft hadron interactions.

The NA60 experiment has collected an unprecedented statistics of 180000 low mass muon pairs inproton-nucleus data at

√s = 27.5~GeV exposing to the beam six target materials: Be, Cu, In, W,

Pb and~U. The very good statistical accuracy and dimuon mass resolution allowed us to perform aprecision measurement of the ρ line shape related the T parameter of the Boltzmann factor, whichwas measured for the first time in p-A collisions. The ρ − ω interference was also investigatedand preliminary results are reported. No evidence of in-medium effects is found. In addition, theelectromagnetic transition form factors of the η and ωmesons were also measured, with a significantprecision improvement with respect to the previous measurements. The ω results, compared to thelatest theoretical developments, still show the presence of an anomaly which is not described bytheory. For the ω and ϕmesons, thanks to the good acceptance coverage, the transverse momentumspectra were measured down to zeropt. Finally, the nuclear dependence of the production cross sections was investigated in terms of thepower law σpA ∝ Aα, and the α parameter was studied as a function ofpt.

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Study of central production in pp-collisions at √s=7 TeV with theALICE experimentAuthor: Xianguo Lu1

1 Physikalisches Institut-Ruprecht-Karls-Universitaet Heidelberg


The ALICE experiment consists of a central barrel covering the pseudo-rapidity range −0.9 < η <0.9 and of additional detectors which can be used to define pseudo-rapidity gaps on both sides(\mbox−3.7 < η < −0.9 and \mbox0.9 < η < 5.1). The low pT threshold of the central barrelgives ALICE a unique opportunity to study the low mass sector of central diffractive production atthe LHC.

ALICE has collected proton-proton collision data at√s = 7 TeV from March to November 2010. I

will report on the analysis of events with a double-gap signature based on this data sample of about4×108 minimum bias events. An enhancement of f0(980) and f2(1270) is seen in these double-gapevents as compared to no-gap events.


Production of neutral pions and eta-mesons in pp collisions mea-sured with ALICEAuthor: Klaus Reygers1

1 University of Heidelberg


The inclusive production of π0 and ηmesons is measured at mid-rapidity in pp collisions over a widetransverse momentum (pT ) range with the ALICE experiment at

√s=900GeV, 2.76~TeV and 7~TeV.

The mesons are measured via two different techniques: with the calorimeters (PHOS and EMCAL)and via photon conversions reconstructed in the Central Tracking System.

A systematic comparison to next-to-leading order pQCD (NLO) calculations for π0 and η mesons aswell as the

√s-dependence of the π0 production is presented. Furthermore, the η to π0 ratio as well

as the corresponding NLO calculations are discussed.

The presented data serves as a baseline both for the decay photon background for direct photonmeasurements as well as for the background of electrons in open heavy flavor measurements. Itwill then be used to calculate the nuclear modification factor, RAA, in heavy-ion collisions withALICE.

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Measurement of the Multiplicity Dependence of J/ψ → e+e− Pro-duction in √s = 7 TeV pp Collisions with ALICE at the LHCAuthor: Frederick Kramer1

1 IKF, Goethe-Universität Frankfurt


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ALICE is the dedicated heavy-ion physics experiment at the Large Hadron Collider (LHC). It is de-signed to provide excellent capabilities to study the Quark-Gluon Plasma (QGP), the deconfinedstate of strongly-interacting matter, in the highest energy density regime opened up by the LHC.Quarkonia, bound states of heavy (charm or bottom) quarks such as the J/ψ, are crucial probes ofthe QGP. Before drawing conclusions on QGP-induced phenomena all non-QGP effects influencingquarkonia yields have to be understood.

ALICE has measured the charged particle multiplicity distribution at √s = 7 TeV pp collisions [1].A good fraction of events feature multiplicities that are of the same order as in central heavy-ioncollisions at SPS energies. Thus, final-state effects present in heavy-ion collisions, such as a pos-sible interaction with comovers [2], might be unveiled at LHC energies studying the multiplicitydependence of J/ψ production in pp collisions.

We will present first results of the multiplicity dependence of J/ψ production in √s = 7 TeV pp colli-sions. The analysis is based on the reconstruction of the channel J/ψ→e+e− using the central barreldetectors of ALICE.

References[1] K. Aamodt et al., “Charged-particle multiplicity measurement in proton-proton collisions at √s= 7 TeV with ALICE at LHC”, EPJ C 68 (2010) 345.[2] A. Capella et al., “J/ψ suppression at √s = 200 GeV in the comovers interaction model”, EPJ C 42(2005) 419.


Charge dependent azimuthal correlations in PbPb collisions at√sNN = 2.76~TeV

Author: Panos Christakoglou1

1 NIKHEF - Utrecht University


Separation of charges along the extreme magnetic field created in non-central relativistic heavy-ioncollisions is predicted to be a signature of local parity violation in strong interactions. We report onresults for charge dependent two particle azimuthal correlations with respect to the reaction planefor Pb-Pb collisions at √sNN = 2.76~TeV recorded in 2010 with ALICE at the LHC. The results arecompared with measurements at RHIC energies and against currently available model predictionsfor LHC. Systematic studies of possible background effects including comparison with conventional(parity-even) correlations simulated with Monte-Carlo event generators of heavy-ion collisions willbe also presented.


Vector meson production in pp collisions at sqrt(s)=7 TeV, mea-sured with the ALICE detectorAuthor: Alessandro De Falco1

1 Univ. + INFN Cagliari


Low mass meson (ρ0, ω, ϕ) production provides key information on the hot and dense state ofstrongly interacting matter produced in high-energy heavy ion collisions. Among them, strangeness

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enhancement can be accessed through the measurement of ϕmeson production, while the measure-ment of the ρ spectral function can be used to reveal in-medium modifications of hadron propertiesclose to the QCD phase boundary. Vector meson production in pp collisions provides a referencefor these studies. Moreover, it is interesting by itself, since it can be used to tune particle productionmodels at the unexplored LHC energy range.

The ALICE experiment at the LHC can access vector mesons produced at forward rapidity throughtheir decays in muon pairs, and at central rapidity in the di-electron decay channel. We presenttransverse momentum spectra of ϕ and ρ+ω mesons at forward rapidity in pp collisions at

√s =

7~TeV, as well as the ϕ absolute production cross section. We will also discuss the first signals andthe analysis prospects for vector meson studies at forward rapidity in Pb-Pb collisions at √sNN =2.76~TeV.

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Constraining Cold Nuclear Matter Effects on J/ψ production inAu +Au CollisionsAuthor: Darren McGlinchey1

Co-author: Anthony Frawley 1

1 Florida State University


Recent results from PHENIX on J/ψ production in d+Au collisionshave shown that J/ψ’s are significantly suppressed at forwardrapidity. This has interesting implications for J/ψ suppression in Au+Au collisions, andmay providean answer to the J/ψ puzzle. We try to constrain these cold nuclear matter (CNM) effects by fittingthe EPS09 parametrization plus a break-up cross section to the PHENIX data in each rapidity range.In contrast to previous work, a stronger than linear dependence of initial-state shadowing on thenuclear thickness is employed to better fit the d+Au data. We extrapolate our results to predict theCNM effects on J/ψ production in Au+Au collisions and compare with the PHENIX results. We findthat some J/ψ suppression remains in central collisions after factoring out the CNM effects and thatthe forward and midrapidity data are now in agreement within uncertainties.


Measurements of Bose-Einstein correlations at LHC with CMS


1 UCLouvain


Bose–Einstein correlations between identical particles are measured in samples of proton-protoncollisions at 0.9 and 7 TeV centre-of-mass energies, recorded by the CMS experiment at the LHC.The signal is observed in the form of an enhancement of number of pairs of same-sign chargedparticles with small relative momentum. The dependence of this enhancement on kinematic andtopological features of the event is studied.

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MEASUREMENT OF SINGLE-MUON AND J/\psi PRODUCTIONAT FORWARD RAPIDITY AS A FUNCTION OF THE COLLISIONMULTIPLICITY IN PP COLLISIONS AT \sqrts = 7 TeVWITHAL-ICEAuthor: Matthieu Lenhardt1

1 Laboratoire de physique subatomique et des technologies associee


Recently, it has been argued that high-multiplicity pp collisions could lead to the formation of highenergy density matter as in heavy ions collisions [1]. Indeed, the charged particle multiplicityreached in pp collisions at the LHC [2] is similar to the one measured in semi-peripheral Cu-Cucollisions at \sqrts_NN = 200 GeV [3].Wewill present the dependence on charged particlemultiplicity of the single-muon and J/\psi \rightar-row \mu^+\mu- yields in pp collisions at \sqrts = 7 TeV. The number of reconstructed tracklets(\eta<1.6) in the silicon pixel detector are exploited to measure the charged particle density at mid-rapidity. Single-muons (p_T>4 GeV/c) from heavy flavoured hadron decays and inclusive J/\psi(p_T>0) yields have been measured with the muon spectrometer (2.5<\eta<4.0). J/\psi yields atmultiplicities five times the average pp multiplicity will be presented.

[1] K. Werner et al. arXiv:1010.0400v1, and K. Werner et al., Phys. Rev. Lett. 106, 122004 (2011)[2] ALICE Collaboration, EPJC: Vol. 68 (2010) 345[3] PHOBOS Collaboration, Phys. Rev. C 83, 024913 (2011)

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Suppression of neutral pion production at large transverse mo-mentummeasuredwith theALICE experiment in PbPb collisionsat √sNN=2.76 TeV

Author: Gustavo Conesa Balbastre1

1 LPSC - Grenoble


TheALICE experiment at the LHChasmeasured the transversemomentum spectra of neutralmesonsvia the two photon decay in pp and Pb-Pb collisions at √sNN=2.76 TeV over a wide transverse mo-mentum range with different subsystems: with the electromagnetic calorimeters PHOS and EMCALand via conversions of the photons in the innermaterial of the experiment to e+e–pairs reconstructedwith the Central Tracking System.

In this talk, the production of neutral pions in pp and Pb-Pb collisions is compared in terms ofthe so called nuclear modification factor, RAA, for different centrality selections of the Pb-Pb datasample.

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Production of nuclei and anti-nuclei in pp and Pb-Pb collisionswith ALICE at the LHCAuthor: Natasha Sharma1

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1 Department of Physics, Panjab University, Chandigarh, India


We present the first results on the production of nuclei and anti-nuclei such as (anti)deuterons,(anti)tritons, (anti)3He and (anti)4He in pp collisions at √s = 7 TeV and Pb-Pb collisions at √sNN= 2.76 TeV. These particles are identified using their energy loss (dE/dx) information in the TimeProjection Chamber of the ALICE experiment. The Inner Tracking System gives a precise deter-mination of the event vertex, by which primary and secondary particles are separated. The highstatistics of over 350 M events for pp and 16 M events for Pb-Pb collisions give a significant numberof light nuclei and anti-nuclei (Pb-Pb Collisions: anti-deuterons ~ 30,000 and anti-alpha ~ 4).The study of these particles will help to understand their production mechanism. Various particleratios obtained from these collisions and their comparison with different predictions from statisticaland coalescence models will also be discussed.

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Charged particle production at large transverse momentum inPbPb collisions at sqrt(s)=2.76 TeV measured with ALICE at theLHC.Author: Jacek Otwinowski1

1 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm-stadt, Germany


The observed suppression of high-pT particle production in heavy-ion collisions is generally at-tributed to energy loss of partons as they propagate through the hot and dense QCD medium. Inclu-sive transverse momentum spectra of primary charged particles in Pb-Pb collisions at sqrt(s)=2.76TeV have been measured by the ALICE Collaboration at the LHC.The data are presented in intervalsof collision centrality. The charged particle spectra are compared to those measured in pp collisionsat the same collision energy, scaled by the number of underlying nucleon-nucleon collisions. Thiscomparison is expressed in terms of the nuclear modification factor R_AA. The results indicate onlyweak medium effects in peripheral collisions, while there is clear evidence for strong medium ef-fects in central collisions. In this talk we will present the results of an analysis of the full Pb-Pbstatistics obtained in the Nov. 2010 run. With these data the transverse momentum range coveredis increased to 50 GeV/c as compared to previous studies of R_AA by ALICE. The evolution of R_AAwith collision centrality and transverse momentum will be discussed.

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Transverse sphericity in minimum bias proton-proton collisionsat

√s = 0.9 and 7 TeV with ALICE at the LHC

Author: Antonio Ortiz Velasquez1

1 Universidad Nac. Autonoma de Mexico (UNAM)


A study of the linearized sphericity in minimum bias proton-protoncollisions at

√s = 0.9 and 7 TeV with the ALICE detector at the LHC is presented. The observable

was measured in the plane perpendicular to the beam direction and using primary charged tracks in|η| ≤ 0.8. The average sphericity as a function of multiplicity is reported for events with differenthardness (soft” andhard”) defined by a cut on the transverse momentum of the leading particle. In

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addition to those studies the average transverse momentum versus multiplicity was measured fordifferent event classes. Data are compared with PYTHIA6 (tunes: ATLAS-CSC and PERUGIA-0),PYTHIA8 and PHOJET.The behavior of the linearized sphericity and of themean pT withmultiplicityindicates that the current event generators tend to “build up” multiplicity by generating more jetswhile on the contrary the data indicate that at high multiplicity the events tend to be more isotropicand the mean pT smaller.

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Measurement of J/psi polarization at forward rapidity in pp col-lisions at sqrt(s)=7 TeV with the ALICE detectorAuthor: Livio Bianchi1

1 Universita degli Studi di Torino-Universita & INFN, Torino-Unkno


The ALICE experiment at the LHC measures quarkonium and open heavy flavour production downto low transverse momentum (pt=0, for quarkonium) at forward rapidity in the muon channel. Inthis scope, the quarkonia and heavy flavour physics program in pp collisions aims to define a propernormalization for nuclear collision studies and to address prominent unresolved issues, such as thedetermination of the quarkonium production mechanism.Polarization is considered as one of the most promising observables to discriminate among all thetheoretical models for quarkonia production.First results on the polarization of J/psi mesons produced at forward rapidity in sqrt(s)=7TeV ppcollisions will be presented.

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Topological reconstruction of strange hadrons in Pb-Pb collisionswith the ALICE experimentAuthor: Marian Putis1

1 Pavol Jozef Safarik University, Kosice, Slovakia


The studies of strange particle production provide information about the dynamics of the systemwhich was created in Pb-Pb or pp collisions at LHC energies. Reconstruction of strange particlesbased on their decay topology allow us to extract yields over a large transverse momentum range(from ~ 0.6 GeV/c up to ~ 8 GeV/c). The ALICE experiment provides high statistics data from proton-proton and Pb-Pb collisions for this study. The analysis is focusing on strange particles K0s andLambdas created in Pb-Pb collisions at sqrt(sNN)=2.76 TeV. The main principles of geometrical re-construction and signal extraction are presented. The efficiency is obtained from Monte - Carlosimulations and used to correct the raw yields. Finally, our latest results related to Lambda and K0sanalysis are presented.

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Inclusive photon production at forward rapidities for pp colli-sions at √s = 0.9 TeV and 7 TeV in ALICE at the LHC

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Author: Sudipan De1

1 Variable Energy Cyclotron Centre (VECC)-Department of Atomic Ene


We report the first measurement of the multiplicity and pseudorapidity distributions of photons inthe pseudorapidity region of 2.3 < η < 3.9 in proton-proton collisions at center of mass energies of 0.9TeV and 7 TeV at the LHC. The photon measurement is dominated by neutral pion decays and thuscomplimentary to those of the charged particles. Multiplicity distributions at both energies followdouble Negative Binomial Distributions (NBD). We observe that the average photon multiplicity in-creases logarithmically with the beam energy. Photon multiplicity and pseudorapidity distributionsfor inelastic and non-single diffractive events are compared with results from event generators (Pho-jet, Pythia). Phojet is close to the data at 0.9 TeV, but both models under-predict the observed dataat 7 TeV. Limiting fragmentation behavior is studied by combining with measurements from otherexperiments and then compared to the models.

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Photoproduction of J/Psi in Ultra-Peripheral Pb+Pb collisions atsqrt(s_NN)=2.76 TeV in ALICEAuthor: Daniele De Gruttola1

1 University and INFN of Salerno - CERN


When two relativistic nuclei collide with impact parameter larger than twice their radius (b>2R_A),they may interact in several ways: nuclear excitation with neutron emission, two-photon exchange,coherent production of vector mesons with pomeron or gluon exchange. These events are usuallyreferred as Ultra Peripheral Collisions (UPC). A relevant process is the production of vector mesonscontaining heavy flavours: this is a powerful tool to study the gluon distribution function in thenuclei, up to x as low as 10^-4. In this presentation we show the performance of the ALICE detectorin the search for J/psi produced in UPC events during the first LHC Pb-Pb run atsqrt(s_NN)=2.76 TeV.The total cross section for this process is a small fraction of the total Pb-Pb cross section, thereforededicated triggers have been used to tag these events both in the barrel and in the forward muonarm. The details of the data analysis, the cut optimization and the first J/psi candidate events areshown.


Diffraction dissociation of protons in proton-proton collisions at\sqrts = 0.9 TeV, 2.76 TeV and 7 TeV with ALICE at the LHCAuthor: Martin Poghosyan1



(for the ALICE Collaboration)

The relative rates of single‐ and double‐ diffractive processes were measured with the ALICE de-tector by studying properties of gaps in the pseudorapidity distribution of particles produced inproton‐proton collisions at \sqrts = 0.9 TeV, 2.76 TeV and 7 TeV. ALICE triggering efficiencies were

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determined for various classes of events, using a detector simulation validated with data on inclu-sive particle production. Cross‐sections were determined using van der Meer scans to measure beamproperties.

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Cold Nuclear Modification of J/psi Production in d+A and A+ACollisionsAuthor: Matthew Wysocki1

1 University of Colorado Boulder


The production of heavy quarkonia in high-energy nuclear collisions is a problem that is still poorlyunderstood, even without the presence of the quark-gluon plasma. The most common method ofcalculation is with nuclear-modified parton distribution functions and a break-up cross section forthe (pre-J/psi) c-cbar pair passing through the nucleus. Calculations of this nature will be presented(as detailed in arXiv:1011.4534) with different assumptions about the geometric dependence of thenuclear modifications, and the results will be compared to the latest PHENIX d+Au experimentaldata. It will be demonstrated that no combination of nPDFs and sigma_breakup, regardless of thenPDF parameter set and the assumed geometric dependence, can simultaneously describe the entirerapidity and centrality dependence of J/psi modifications in d+Au collisions at sqrt(s_NN) = 200 GeV.Wewill also extend the calculations to include a simple model of initial-state parton energy loss, withthe same result. We will then compare the results of these calculations with others using coherentJ/psi production and gluon saturation at low x. Finally, we will project these calculations to Au+Aucollisions at sqrt(s_NN) = 200 GeV, and compare to the latest experimental data for that case.

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Measurement of inclusive neutral pion yields in in p+p andPb+Pbcollisions at √sNN=2.76 TeV with the ALICE EMCalAuthor: Ermes Braidot1

1 Lawrence Berkeley National Lab. (LBNL)


We present the measurement of inclusive differential π0 yields in p+p and centrality-selected Pb+Pbcollisions at √sNN = 2.76TeV, using the large-acceptance ALICE Electromagnetic Calorimeter(EMCal). The recently completed EMCal enhances ALICE capabilities for the study of jets, neutralmesons, electrons, and direct photons. The EMCal acceptance (110 degrees in azimuth, |η|0.7) andhigh granularity enable the reconstruction of neutral mesons over a wide transverse momentumrange, employing invariant mass, shower-shape, and conversion techniques. We present first mea-surement of π0RAA for both peripheral and central Pb+Pb collisions, normalized by the π0 yieldmeasured in p+p collisions at √sNN = 2.76TeV.

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Nonequilibrium effects at the phase transition in chiral fluid dy-namics including dissipation and noise

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Author: Marlene Nahrgang1

Co-authors: Marcus Bleicher 2; Stefan Leupold 3

1 Goethe-University Frankfurt and Frankfurt Institute for Advanced Studies (FIAS)2 Frankfurt Institute for Advanced Studies (FIAS)3 Uppsala University


We present a dynamic study of nonequilibrium fluctuations and correlations at the chiral phase tran-sition starting from the linear sigma model with constituent quarks.Within the formalism of the two-particle irreducible (2PI) effective action the nonequilibrium dy-namics of the sigma field coupled to the fluid dynamic expansion of quarks is obtained consistently.We derive the Langevin equation for the sigma field with the explicit damping coefficient and thenoise terms, which are similar to those we obtain from the influence functional method. The 2PIeffective action in addition contains information about the local equilibrium properties of the quarkfluid like the energy density and the pressure, which are needed for the equation of state. We gobeyond existing studies of Langevin dynamics at the chiral phase transition by putting special em-phasis on the properties and the evolution of the heat bath. The damping in the dynamics of thesigma field leads to energy dissipation from the field to the fluid. In the exact formalism of the 2PIeffective action a conserved energy-momentum tensor can be constructed.Investigating the coupled dynamics of the sigma field and the expansion of the quark fluidwe presentresults on the intensity of sigma fluctuations and the correlations at the critical point and the firstorder phase transition observing strong nonequilibrium fluctuations and correlations.


High-pT suppression of Lambda and K0s in PbPb collisions atsqrt(sNN) = 2.76 TeV with ALICEAuthor: Simone Schuchmann1

1 Institut fuer Kernphysik-Johann-Wolfgang-Goethe Univ.


Significant suppression of unidentified charged particles at large transverse momentum has beenobserved in central Pb-Pb collisions at the LHC.Measurements of identified particles will provide more detailed information on the suppressionmechanism. The production of Lambda and K0s at mid-rapidity in pp and Pb-Pb at sqrt(sNN) =2.76 TeV is studied with the ALICE detector at the LHC. Lambda and K0s are measured by recon-structing their weak decays into charged hadrons, employing the tracking capabilites of the ALICEcentral barrel. The analysis of Lambda and K0s production in Pb-Pb is performed in intervals of thecollision centrality and compared to results from pp at the same collision energy. We discuss thecentrality dependence with particular emphasis on strange particle suppression at high pT.


Triggered di-hadron correlations in PbPb collisions from the AL-ICE experimentAuthor: Andrew Adare1

1 Yale University

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Angular correlations between unidentified hadron trigger andassociated particles are measured by the ALICE experiment for 0.5 < p

(t),(a)t < 15 GeV/c, where

p(t)t > p

(a)t . The

modification of conditional yields in central Pb–Pb collisions ismeasured with respect to p–p (IAA) and with respect to peripheralevents (ICP ). Significant suppression is observed on the sideopposing the trigger, while an enhancement is measured on the nearside. The latter result is a notable departure from RHIC measurements.In addition, the shape of the pair azimuthal distribution is examinedin a variety of centrality categories for pairs in |η| < 0.8where |η(t) − η(a)| > 0.8. A set of two-particle Fouriercomponents Vn∆ ≡ ⟨cos(n∆ϕ)⟩ arecomputed directly from the long-range azimuthal correlationfunctions. A series including V1∆ to V5∆ describesthe data. For each n, a fit is applied over all pT binssimultaneously to test the collectivity hypothesis Vn∆ ≃ v

(t)n v

(a)n . This factorization hypothesis is

satisfied atlow pT but not at higher pT . The divergence between the dataand the global fit provides a new measure of the onset of nonflowdominance in long-range correlations due to the away side jet. Thefirst five single-particle vn coefficients are presented as newresults from the global fit, and are compared to vn valuesmeasured by more established methods.

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Elliptic Flow from the Parton-Hadron-String-DynamicsAuthors: Elena Bratkovskaya1; Vadim Voronyuk2; Viacheslav Toneev2; Volodymyr Konchakovski3; WolfgangCassing3

1 Institute for Theoretical Physics, Frankfurt University2 Dubna, JINR3 Institute for Theoretical Physics, Giessen University


Wepresent a systematic study of correlations in pseudorapidity and azimuthal angle for charged hightransverse momentum hadrons in heavy-ion collisions at the top RHIC energy within the Parton-Hadron-String-Dynamics (PHSD) transport approach. The study shows that a significant part (60%)of the high-pT hadron attenuation seen experimentally can be attributed to inelastic interactions of‘leading’ pre-hadrons with the dense hadronic environment. The presence of partonic phase leadsto larger suppression of ‘far-side’ correlations which agrees with available data. We find also a fairdescription of the elliptic flow of charged hadrons as a function of the energy of the reaction, itscentrality and the transverse momentum pT within PHSD approach. Furthermore, an approximatequark-number scaling of the elliptic flow v2 of hadrons is observed in the PHSD results, too. Thus weconclude that partonic phase plays significant role for the both: high-pT correlations and collectiveflow.

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Multiplicity Dependent Di-Hadron Correlations Measured withALICE at the LHCAuthor: Eva Sicking1

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1 Universität Münster / CERN


A Large Ion Collider Experiment (ALICE) is the experiment at the Large Hadron Collider (LHC)optimized for heavy-ion collisions. However, ALICE is also studying pp collisions which not onlyprovides important reference measurements but is also part of a stand-alone pp physics program.In particular, high multiplicity pp collisions are an interesting field of study of particle productionmechanisms.

Here we present the results of a di-hadron angular correlation analysis which has the aim to mea-sure the number of multi-parton interactions and mini-jet fragmentation properties as a functionof multiplicity. We discuss the problems encountered with standard correlation measurements athigh multiplicities and present solutions to cope with these. Results are compared between dif-ferent center of mass energies. Also, comparisons between different Monte Carlo generators arediscussed.

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Anomalous baryon production and its interplay with jet energyloss at RHIC and LHC energiesAuthor: Peter Levai1

Co-authors: Attila Pasztor 2; Daniel Berenyi 2; Vladimir V. Skokov 3

1 KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary2 Eötvös University, Budapest, Hungary3 GSI, Darmstadt, Germany


The study of the nuclear suppression factor of charged hadrons and neutral pions in AuAu collisionsat RHIC energies indicated the possible appearance of an anomaly at higher pT-s: although protonsare expected to be produced from gluons, but jet energy loss is less effective for them comparing topion suppression. Fragmentation function and jet energy loss based explanation can not reproducethis phenomena, which opens a discussion on anomalous baryon production at high-pt. We investi-gated the appearance of non-perturbative hadron production channels connected to the formation ofstrong non-abelian fields, and their strength at RHIC and LHC energies. We performed calculationswith time dependent strong fields and studied the quark-pair and diquark-pair production at high-pTto produce leading quarks and diquarks to be hadronized. The numerical results are presented anddiscussed.

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A data driven validation of the Pythia jet cross section in pp col-lisions at

√s = 2.76 TeV

Author: Hermes Leon Vargas1

1 IKF Goethe-Universität Frankfurt am Main


Studies of the inclusive jet production in Pb-Pb collisions at√s = 2.76 TeV and its possible modi-

fication by the hot and dense medium, require a comparison of the measured jet spectrum to thatfrom pp collisions at the same center of mass energy. The goal of our study is to validate a reference

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spectrum obtained via Pythia simulations, using jet cross section measurements at the Tevatron andthe LHC.We present comparisons of data driven extrapolations and interpolations with the predictions fromPythia6, using the tune Perugia-0.

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Charged KK femtoscopy correlations from 7 TeV pp collisionsmeasured by ALICE collaboration.Author: Ludmila Malinina1

Co-author: ALICE for the ALICE Collaboration 2

1 Joint Inst. for Nuclear Research (JINR)-Unknown-Unknown2 CERN


Charged KK femtoscopy correlations from 7 TeV pp collisionsmeasured by ALICE collaboration.

L. Malinina (SINP MSU-JINR) for the ALICE collaboration

We report on the results of charged kaon femtoscopy analysis of the 7 TeV pp collisions at the LHCin the ALICE experiment. KK correlation functions are constructed in 3 multiplicity and 4 kt bins.The KK source parameters are extracted by fitting thecorrelation functions with Gaussian, describing the source, multiplied by a polynomial backgroundfunction with free coefficients (baseline). The contributions to the systematicerrors from the baseline choice have been studied. The weak increase of the KK Rinv with multiplic-ity and some evidence on the decrease with kt was observed in kt range (0.2-0.8) GeV/c. For the ktdependence, the charged kaons are found to be complimentary to the neutral ones in their coverageof a larger range in kt (0.2-2.0) GeV/c and a decrease in the Rinv is observed for increasing kt as it isalso seen in identical two-pion correlations in these collisions.


Untriggered di-hadron correlations in PbPb \sqrts_NN =2.76TeV collisions from the ALICE experimentAuthor: Anthony Timmins1



We present measurements of untriggered di-hadron correlations as a function of centrality in Pb-Pb\sqrts_NN =2.76 TeV collisions, for charged hadrons with p_T > 0.15 GeV/c. These measure-ments provide a map of the bulk correlation structures in heavy-ion collisions. Contributions tothese structures may come from jets, initial density fluctuations, elliptic flow, and/or momentumconservation. We will decompose the measured correlation functions via a multi-parameter fit inorder to extract the soft ridge; the long range \delta(\eta) correlation on the nearside observed atRHIC energies. The effect of including higher harmonics (v_3 and v_4) in this procedure will bediscussed. We will compare our results to various theoretical predictions based on differing schemesfor the initial conditions. Finally, wewill investigate empirical scalings (such as the number of binarycollisions) for the various contributions as a function of centrality, which may also help determinetheir origin.

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Measurement of Upsilon suppression in Au+Au collisions at 200GeVAuthor: Shawn Whitaker1

1 Iowa State University


Measuring states in the charmonium and bottomonium families is predicted to provide an indica-tion of the temperature of the quark gluon plasma. In a hot medium less tightly bound states arepredicted to be dissociated at lower temperatures than the more tightly bound ground states.Understanding quarkonium suppression mechanisms of the QGP is one of the outstanding chal-lenges for theorists and experimentalists at RHIC and the LHC.PHENIX has made detailed measurements of J/ψ suppression in forward and in mid-rapidity. Alarge sample of Au+Au collisions at

√SNN=200 GeV was collected during 2010 data taking run at

RHIC.From this sample, Upsilon mesons at mid-rapidity were identified in the di-electron decay channeland were studied to calculate their nuclear modification factor relative to that of the Jψ.

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Evaluation of the identification efficiency of the ALICE HMPIDdetector in p-p collisions at √s = 7 TeV bymeans of V0 decaysAuthor: Francesco Barile1

1 Universita degli Studi di Bari-Universita e INFN


The ALICE experiment, dedicated to the study of heavy-ion collisions at LHC energies, features ahigh-quality particle identification system, based on the the Inner Tracking System (ITS), the Time-Projection-Chamber (TPC), the Time-of-Flight (TOF) and the HMPID. The ALICE-HMPID (HighMomentum Particle Identification detector) has been designed to identify charged pions and kaonsin the range 1< p <3 GeV/c and protons in the range 2< p<5 GeV/c, in a reduced region of the phasespace. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters,with a total active area of 11 m2, which exploit the technology of large area MWPCsequipped with Cesium Iodide (CsI) photo-cathodes for imaging the Cherenkov light emitted by aliquid C6F14 radiator. Since November 2009 ALICE is collecting p-p and Pb-Pb collisions data atLHC. A study of the particle identification efficiency of the HMPID has been carried out with samplesof protons and pions coming from reconstructed V0 (Λ/anti-Λ, K0S) decays in p-p collisions at √s =7 TeV.

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Energy dependence of π0 suppression in Au+Au collisionsAuthors: Baldo Sahlmueller1; Ondrej Chvala2

1 Stony Brook University2 UCR Riverside

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Previous RHIC results have shown that high-pT mid-rapidity π0 and η mesons are suppressed incentral Au+Au collisions while they are not in d+Au collisions. Furthermore, direct photons inAu+Au collisions appearmostly unsuppressed aswell, with a possible exception at very high pT . Thisleads to the picture of a hot and dense medium in the final state. Measurements of d+Au collisionsare crucial to understand the initial state in heavy-ion collisions. New d+Au data taken in 2008improve the integrated luminosity by a factor of about 20 over the data from the 2003 run. This dataset will allow much better constraints of the initial state and improve the significance of the directphoton measurement at high pT . We will present the current status of the analysis and preliminaryresults on the production of π0, η, and direct photons and discuss the interpretation of the resultsin the light of the results from Au+Au collisions.

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Theinfluence of bulk evolutionmodels onheavy-quarkphenomenol-ogyAuthor: Pol Gossiaux1

Co-authors: Hendrik van Hees 2; Jörg Aichelin 1; Marcus Bluhm 1; Min He 3; Ralf Rapp 3; Sascha Vogel 1

1 Subatech2 Institut für Theoretische Physik, Universität Giessen3 Cyclotron Institute and Department of Physics and Astronomy, Texas A&M University


Heavy quarks are considered as one of the essential probes to study the interior of a QGP.The exper-imental observables contain only the combined information about the expansion of the system andthe elementary interaction of heavy quarks with the plasma constituants. In order to asses the latter,we have to understand the influence of different expansion scenarios on the observables. In practice,models proposed by various groups for interpreting RHIC heavy quark data should be thoroughlycompared before one can progress towards the understanding of LHC data. In this contribution wereport on the joint effort of SUBATECH and TAMU in this respect: We study the impact of differ-ent Quark-Gluon Plasma expansion scenarios in heavy-ion collisions on spectra and elliptic flowof heavy quarks. For identical heavy-quark transport coefficients relativistic Langevin simulationswith different expansion scenarios can lead to appreciable variations in the calculated suppressionand elliptic flow of the heavy-quark spectra, by up to a factor of two. A cross comparison with twosets of transport coefficients supports these findings, illustrating the importance of realistic expan-sion models for quantitative evaluations of heavy-quark observables in heavy-ion collisions. It alsoturns out that differences in freeze-out prescriptions and Langevin realizations play a significantrole in these variations. Light-quark observables are essential in reducing the uncertainties associ-ated with the bulk-matter evolution, even though uncertainties due to the freeze-out prescriptionpersist.

Ref: arXiv:1102.1114, submitted to PRC

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Azimuthal anisotropy of neutral pion production in Pb+Pb colli-sions at sqrt(s_NN) = 2760 GeV measured by ALICEAuthor: Dmitry Blau1

1 RRC Kurchatov Institute


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The measurement of the azimuthal anisotropy of neutral pions at hightransverse momentum helps unveil the path-length dependence ofjet-quenching. A further motivation to study this anisotropy at LHCenergies is given by the fact that the azimuthal anisotropy of neutral pions at RHIC is under-predictedby current QCD energy-losscalculations. The neutral pion yield as a function of the emissionangle w.r.t. the reaction plane is measured with the ALICE PHOS andEMCAL calorimeters as well as by reconstructing photons via theirconversion into e+e− pairs. In addition to the azimuthalanisotropy of neutral pions the reaction plane dependence of thenuclear modification factor, RAA, is presented.

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Modeling heavy ion collisions with CHIMERAAuthor: Irakli Garishvili1

Co-authors: Andrew Glenn 1; Betty Abelev 1; Loren Linden Levy 1; Michael Cheng 1; Ron Soltz 1

1 Lawrence Livermore National Laboboratory


Precisely determining the essential properties of QGP, such as the ratio of shear viscosity to en-tropy density, eta/s, initial temperature, T_init, and energy density remains among the greatestchallenges in the field of heavy ion physics.

To constrain these properties we have developed a software framework CHIMERA that is designedto perform statistical evaluation of multiple QGP signatures by comparing results from our multi-stage hydrodynamics/hadron cascade model of heavy ion collisions to the key soft observables (HBT,elliptic flow, spectra) measured at RHIC and LHC. All relevant data from different experiments areconveniently compiled into a single format. The unique feature of CHIMERA is that it utilizes bothstatistical and systematic uncertainties.

The hydrodynamics/hadron cascade model used in the framework incorporates different initial stateconditions, pre-equilibrium flow, the UVH2+1 viscous hydro model, Cooper-Frye freezeout, theUrQMD hadronic cascade model, and the Correlation After Burner (CrAB). To test the sensitivityof the observables to the equation of state (EoS), we use several different EoS in the hydrodynamicevolution, including those derived from the hadron resonance gas model and lattice QCD.

For a particular selection of initial conditions and pre-equilibrium flow we consider T_init-eta/sgrid. For each grid point and a particular observable we evaluate the extent of agreement betweenthe model and experimental data by calculating chi-squared variable. The latest CHIMERA resultsare presented.


Identified particles from viscous hydrodynamicsAuthor: Denes Molnar1

1 Purdue University


Much of our understanding of the collision dynamics at RHIC and LHC relieson contrasting hydrodynamic or hydro+transport calculations with

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experimental data. For example, early evidence for rapid thermalizationand quark-gluon plasma phase transition at RHIC came from particle spectraand the pion-proton splitting of differential elliptic flow. An inevitablecomponent in these calculations is the conversion of the fluid toparticles. For an ideal fluid the conversion is straightforward (the usualcaveats of the Cooper-Frye treatment aside) because the phase spacedistributions are locally thermal for each species. For a viscous fluid,however, an infinite class of phase space corrections can reproduce thesame hydrodynamic variables, even in a one-component system.

Present viscous hydrodynamic calculations routinely assume that phasespace corrections induced by shear stress are quadratic in momentum andthat they have the same coefficient for all particle species (”democratic”Grad ansatz), independently of microscopic details. However, in a gas ofhadrons, equilibration is driven by scattering rates - species thatscatter rarely tend to be further away from local equilibrium than thosethat scatter often.

We will present results from fully nonlinear covariant transport theoryfor the phase space corrections in an expanding multicomponent gas, andtest the validity of Grad’s quadratic ansatz and of the “democratic”assumption for sharing viscous effects between species. The findings willbe compared to phase space corrections from linear response theory, whichis applicable for small gradients and small deviations from localequilibrium. Finally, we will show how dynamical phase space correctionsaffect basic identified particle observables (spectra and elliptic flow)in the framework of viscous hydrodynamics.

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The Rise and Fall of the Ridge at RHIC and the LHCAuthor: Paul Sorensen1

Co-authors: Agnes Mocsy 2; Boris Bolliet 3; Navneet Pruthi 4; Yadav Pandit 5

1 BNL2 Pratt Institute3 ENS de Lyon4 Panjab University5 Kent State University


Recent data from heavy ion collisions at RHIC show unexpectedly large near-angle correlations thatbroaden longitudinally with increasing centrality. The amplitude of this ridge-like correlation risesrapidly, reaches a maximum, and then falls in the most central collisions. In this talk we explain howthis centrality dependence arises from an interplay between initial state density fluctuations and thealmond shape of the overlap region. We show that the disappearance of the almond shape in centralcollisions leads to the observed reduction in the near-side ridge, uniquely linking the ridge to initial-state coordinate-space anisotropies converted into final-state momentum-space correlations. Weshow how the width of the ridge is related to length scales in the expanding system and we providea prediction for the ridge amplitude in Pb+Pb collisions at √sNN = 2.76 TeV.

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Three particle correlations as a probe of eccentricity fluctuations

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Author: Jim Thomas1



The geometrical overlap region in non-central heavy ion collisions is almond shaped. Due to thisshape profile, density fluctuations for different harmonics are strongly correlated; for example v1and v3. If the final momentum space distributions in heavy-ion collisions depend on the initialdensity, then the coupling of different harmonics will lead to three particle correlations such ascos(phi_1+2phi_2-3phi_3). In this posterwe present STARmeasurements of cos(phi_1+2phi_2-3phi_3)as a function of pt and centrality in √

sNN = 200 GeV Au+Au collisions. We compare our results topredictions from Teaney and Yan (1) based on ideal hydrodynamic calculations.

(1) D. Teaney and L. Yan, arXiv:1010.1876v1 [nucl-th]

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Heavy ion initial conditions and correlations between highermo-ments in the spatial anisotropyAuthor: Michael McCumber1

1 University of Colorado

Fluctuations in the initial conditions for relativistic heavy ion collisions are proving to be crucialto understanding final state flow and jet quenching observables. The initial geometry has beenparameterized in terms of moments in the spatial anisotropy (i.e. e2, e3, e4, e5, …), and it has beenstated in multiple published articles that the vector directions of odd moments are uncorrelated withboth the even moments and the reaction plane angle. This poster details the results from a MonteCarlo Glauber calculation (available in arXiv:1011.1853v1) where these statements are shown to beincorrect. Instead a substantial nonzero correlation is found to be present between the even and oddmoments in peripheral Au+Au collisions where the number of participating nucleons is small. Thedependence of the correlation between the higher moments will be shown as a function of centralityand beam species.


Measurement of the electromagnetic dissociation cross-sectionof Pb nuclei at 2.76 A Tev with the ALICE ZDCAuthor: Chiara Oppedisano1

1 INFN, Sezione di Torino


Electromagnetic dissociation of heavy nuclei in ultra-peripheral interactions at high energies can beused to monitor the beam luminosity at colliders.Neutrons emitted by the excited nuclei close to beam rapidity are detected by the ALICE Zero DegreeCalorimeters (ZDC) with full acceptance, providing a precise measurement of the event rate.

During the 2010 Pb-Pb run, a dedicated data taking has been performedtriggering on electromagnetic processes with the ZDC. These data, combined with the results fromthe Van derMeer scan, allow one tomeasure the dissociation cross-section of Pb nuclei at sqrt(s)=2.76A TeV.

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Experimental results on the cross-section for electromagnetic dissociation processes of Pb nuclei atthe LHC will be presented together with a comparison to the available predictions.


Elliptic and triangular flow of identified particles measured withthe ALICE detector.Author: Mikolaj Krzewicki1

1 NIKHEF


The anisotropic flow of identified particles is an important observable to test the collective behaviorof the matter created in heavy-ion collisions. We report on the first measurements of elliptic andtriangular flow for charged pions, kaons and protons in lead-lead collisions at 2.76 TeV per nucleonpair center of mass energy, measured with the ALICE detector at the LHC.

We will make a detailed comparison of the observed mass splitting of v_2 at LHC energies to RHICmeasurements at lower energies. For identified particles with intermediate transverse momenta wetest the quark coalescence picture with v_2 and v_3 scaled by the number of constituent quarksvs scaled p_t and scaled m_t.

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Jet production measurements with the ALICE Experiment in ppcollisions at the LHCAuthor: Sidharth Kumar Prasad1



Measurements of inclusive jet production cross sections in proton-proton (pp) collisions provide adirect test of predictions of perturbative quantum chromodynamics. They also provide a baseline formeasurements in heavy ion collisions. Jets are the collimated spray of particles originating from thefragmentation of hard scattered partons in the collision. They are defined by clustering algorithms ineach event and represent the physical properties of partons from the hard scattering. It is thereforeimportant to understand the performance of clustering algorithms that can be used in pp and A-Acollision studies.

The ALICE detector at the LHC has excellent tracking capabilities for charged particles over a widerange of transverse momenta and can be used for studying jet properties. We will present the per-formance of kt, anti-kt, SISCone and UA1 cone finder clustering algorithms for charged particle jetreconstruction using the ALICE detector at midrapidity in proton-proton collisions at the LHC. Wewill also compare our results with PYTHIA simulations.

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Measurement of ChargeMultiplicity Asymmetry Correlations toSearch forChiralMagnetic Effect inHeavy IonCollisions by STAR

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Author: Quan Wang1

1 Purdue University


It has been suggested that local parity violation in QCD would lead to charge separation of quarksby the Chiral Magnetic Effect (CME) in heavy ion collisions.Charge separation could yield a dynamical charge multiplicity asymmetry with respect to the reac-tion plane.In this poster, we report results on charge multiplicity asymmetrycorrelations in √

sNN = 200 GeV Au+Au and d+Au collisions by the STAR experiment, as well asfrom the RHIC beam energy scan.We found that the correlation results could not be explained by CME alone.To gain further insights, we study our results as a function of themeasured azimuthal angle range as well as the event-by-event anisotropy parameter v2.The results indicate that the charge separation effect appears to bein-plane rather than out-of-plane.We found that the charge separation effect is proportional to theevent-by-event v2 and consistent with zero in events with v2 ≈ 0.Our studies suggest that the charge separation effect, within thestatistical error, may be a net effect of event anisotropy and correlated particle production.Possible upper limit on the CME imposed by our data will be discussed.

584

Ridge Studies in Pb+Pb Collisions at the LHC based on Numberand Transverse Momentum Two-Particle Correlation Functions

Author: Claude Andre Pruneau1

1 Wayne State University-Unknown-Unknown


Observations of a ridge on the near-side, and a dip on the away-side of two-particle correlationsmeasured in central Au + Au collisions have generated considerable interest at RHIC. Are the twophenomena connected? Do they result from jet interactions with the medium, or do they naturallyarise from the rapid thermalization and hydrodynamic expansion of collision systems subject tolarge initial fluctuations?We present measurements, carried with the ALICE detector, of number (R2) and transverse momen-tum (∆pt∆pt) correlation functions in Pb + Pb collisions. The two correlation functions are studiedas a function of collision centrality for ++, -\ -, and +- charged particle pairs in various momentumranges. The like-sign and unlike-sign correlations exhibit a different evolution with collision cen-trality. We combine these correlations to study charge dependent (CD) and charge independent (CI)correlation functions. We characterize these distributions by studying Fourier decompositions of∆φ projections of the R2 and ∆pt∆pt correlation functions for different ranges of ∆η. Of partic-ular interest are the evolution of the ratios of 3rd, and 4th harmonics to the 2nd harmonics withnumber of participants. We will discuss these results in light of a MC Glauber model of the initialeccentricity of collision nucleon participants.

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Charge Fluctuations in Pb-Pb Collisions at √sNN = 2.76 TeV mea-sured by ALICE experimentAuthor: Satyajit Jena1

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1 IIT Bombay


Charge fluctuations are considered to provide a possible signature for the existence of the de-confinedQuark Gluon Plasma phase (QGP). Charge fluctuations are sensitive to the number of charges in thesystem, thus the fluctuations in the QGP, with fractionally charged partons, are significantly differ-ent from those of hadron gas with unit charged particles [1,2]. The study of charge fluctuations havebeen carried out by using the variable, ν+-,dyn [3] which, by its construction, is free from the col-lisional bias, i.e., impact parameter fluctuations and fluctuations from the finite number of chargedparticles within the detector acceptance. The dependence of charge fluctuations on the rapidity win-dows for various centrality bins are analyzed for Pb+Pb collisions at √sNN =2.76 TeV in the ALICEexperiment at CERN-LHC. A scaling behavior is observed as a function of increasing pseudo-rapiditywindow for the charge fluctuations, expressed in terms of Nch x ν+-,dyn, where Nch is the numberof charged particles. The observed fluctuations are corrected for diffusion of fluctuations [4,5] in thehadronic medium. The results will be shown and discussed.

[1] S. Jeon, V. Koch, Phys. Rev. Lett. 85 (2000) 2076[2] M. Asakawa,U.W. Heinz, and B. Muller, Phys. Rev. Lett., 85 (2000) 2072[3] C. Pruneau, S. Gavin, and S. Voloshin, Phys.Rev.C66:044904,200[4] E. V. Shuryak and M. A. Stephano, Phys. Rev. C63 (2001) 064903[5] M. A. Aziz and S. Gavin, Phys. Rev. C70 (2004) 034905.

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Towards the phase diagram of QCDAuthor: Rainer Stiele1

Co-authors: Jan M. Pawlowski 1; Jürgen Schaffner-Bielich 1; Lisa Marie Haas 1

1 Institute for Theoretical Physics, Heidelberg University

Lattice computations as well ab initio continuum QCD calculations show a broad crossover for bothchiral symmetry restoration and the deconfinement transition at vanishing density. Particularly,the change of the order parameter for deconfinement, the Polyakov loop, occurs in a rather broadtemperature interval. In contrast, current Polyakov loop extended effective models show steeperslopes in a smaller transition region. Moreover, the critical temperatures show some dependence onthe chosen Polyakov loop potential. We qualitatively improve these models towards full QCD byadjusting the Polyakov loop potential to the full glue potential of continuum ab initio computations.We present results for the phase structure of QCD at finite density derived from these improvedmodels.


Femtoscopy of the system shape fluctuations in heavy ion colli-sionsAuthor: Sergei Voloshin1

1 Department of Physics and Astronomy-College of Science-Wayne Sta


The system created in a heavy ion collision in general is not azimuthally symmetri; moreover, theinitial spatial distribution, e.g. that of the energy density, fluctuates event-by-event even at fixed im-pact parameter. Because of particle interactions, this initial spatial asymmetry leads to anisotropies

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in particle emission – the phenomenon called anisotropic flow. The best known anisotropy of thiskind is the elliptic flow that is described by the second harmonic in particle azimuthal distribution.Recently, the so-called triangular, and higher harmonic flow, and in particular their sensitivity to thesystem initial conditions attracted a lot of attention, as they might provide additional important in-formation about the initial conditions and dynamical properties (e.g. viscosity) of the system.

Fluctuations in the initial geometry should be also reflected in the detail shape of the system atfreeze-out. In this talk I discuss the possibility to measure such fluctuations by means of identicaland non-identical particle femtoscopy. I support my conclusion on the sensitivity of the method tomeasure triangularity and higher harmonic spatial asymmetries by analytical calculations, and byresults from event generators and blast wave model calculations.


Two-pion Bose-Einstein correlations in PbPb collisions at 2.76TeV with ALICEAuthor: Jorge Mercado1


We present the first measurement of pion source radii in Pb-Pbcollisions at the LHC. The radii were obtained by analyzing theBose-Einstein enhancement in two-pion correlation functions. Like at lower energies, the radii dropwith increasing transverse momentum, indicating the presence of collective expansion. In absoluteterms, all three radii (R_out, R_side, R_long) are larger than at RHIC, roughly consistent with a linearscaling with the cube root of the particle multiplicity. The results, taken together with those obtainedfrom the study of the multiplicity and the azimuthal anisotropy, indicate that the fireball formed innuclear collisions at the LHC is hotter, lives longer, and expands to a larger size as compared to lowerenergies.

Jets / 589

Probing nuclear matter with jets and γ-hadron correlations: re-sults from PHENIXAuthor: Nathan Grau1

1 Augustana College


Fully reconstructed jets and hadrons correlated with a direct photon significantly reduce energy-loss bias, the bias toward measuring particles from partons which suffer little energy loss. In d+Aucollisions, one accesses the physics at large x, which yields important constraints for nuclear par-ton distribution functions. In both d+Au and A+A collisions, coherent multiple-scattering modelsof energy loss can be tested. In this contribution, we present the current results from the PHENIXexperiment on fully reconstructed jets and direct γ-hadron correlations. Baseline measurements ofjets in p+p collisions as well as their yield and correlation modifications in d+Au and Cu+Cu willbe given. From γ-hadron correlations, we present the fragmentation function in p+p and Au+Aucollisions and its modification in Au+Au to lower zT than what has previously been studied. Impli-cations of this data on our understanding of both cold and hot, dense nuclear matter created at RHICare discussed.

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Status of the Search for Hadronic Squeezed Correlations at RHICEnergiesAuthor: Sandra S. Padula1

Co-authors: Danuce M. Dudek 1; Otavio Socolowski, Jr. 2

1 Instituto de Fisica Teorica (IFT)-Univ. Estadual Paulista, SP, Brazil2 IMEF - Univ. Federal de Rio Grande, RS, Brazil


The hot and dense medium formed in high energy heavy ion collisions may induce shifts of hadronicmasses from their asymptotic values. In case this mass modification indeed occurs, it was demon-strated that squeezed correlations of particle-antiparticle pairs, also known as Back-to-Back Correla-tions (BBC), should appear. They are expected either in the bosonic (bBBC) or in the fermionic (fBBC)cases [1], in both being positive correlations of unlimited intensity, even for finite-size systems ex-panding with moderate flow [2]. Although they could nicely probe the mass shift with asymptoticparticles, these hadronic squeezed correlations are very sensitive to the functional form of theirtime emission distribution. This strong sensitivity was demonstrated in [1], by comparing the sud-den emission with a Lorentzian distribution, which reduced the intensity of the effect by orders ofmagnitude. We show here that the reduction of the signal is evenmore dramatic if this time emissionis parameterized by a Levy-type of distribution [3], although it could still survive if the duration ofthe process is short and if we search for the effect with lighter mesons, such as kaons.

To experimentally search for the BBC signal, we have suggested to look for the particle-antiparticlesqueezed correlation function, plotted in terms of the average momentum of the pair, K12 = (k1 +

k2)/2, for high values of their relative momentum, q12 = (k1−k2) [4]. The first experimental searchfor the squeezed particle-antiparticle correlations was shown for different hadron pairs in Ref. [5].We compare here such preliminary results with predictions of our model forK+K− pairs, showingthat the outcome of the experimental search may be still inconclusive, however it does not deny theexistence of the squeezing effect on kaons produced at RHIC energies with in-medium modifiedmasses.

[1] M. Asakawa, T. Csorgo, M. Gyulassy, Phys. Rev. Lett. 83, 4013 (1999); P. K. Panda, T. Csorgo, Y.Hama, G. Krein, and Sandra S. Padula, Phys. Lett. B 512, 49 (2001).[2] Sandra S. Padula, G. Krein, T. Csorgo, Y. Hama, and P. K. Panda, Phys. Rev. C 73, 044906 (2006).[3] Danuce M. Dudek and Sandra S. Padula, Phys. Rev. C 82, 034905 (2010).[4] Sandra S. Padula, O. Socolowski Jr., T. Csorgo and M. I. Nagy, Proc. Quark Matter 2008, J. Phys.G: Nucl. Part. Phys. 35, 104141 (2008); Sandra S. Padula and Otavio Socolowski Jr., Phys. Rev. C 82,034908 (2010).[5] Marton Nagy (for the RHIC/PHENIX Collaboration) “Particle-antiparticle back-to-back correla-tionmeasurement in√sNN = 200GeVAu+Au collisions”,WPCF 2009, https://indico.cern.ch/conferenceTimeTable.py?confId=54173#all.

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Dmesonnuclearmodification factors inPbPb collisions at√sNN =2.76 TeV, measured with the ALICE detectorAuthor: Andrea Rossi1

1 Sezione di Padova (INFN)-Universita e INFN


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The comparison of heavy flavour production in proton-proton and heavy-ion collisions allows toprobe the properties of the high-density QCD medium formed in the latter and to study the mech-anism of in-medium partonic energy loss. The ALICE experiment has measured the D meson pro-duction in pp and Pb–Pb collisions at the LHC at

√s = 7 and 2.76 TeV and √

sNN = 2.76 TeVrespectively, via the exclusive reconstruction of hadronic decay channels. The D meson decay ver-tices, displaced by few hundred microns from the main interaction point, are selected by exploitingthe high-resolution tracking performance and the hadron identification capabilities of the ALICEdetectors. The analyses of the D0 → K−π+ and D+ → K−π+π+ channels will be described andthe preliminary results for the D0 and D+ nuclear modification factor will be presented.

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Transversemomentum distributions of pions, kaons and protonsfor high multiplicity and close to azimuthal isotropic events in 7TeV pp collisions with the ALICE experiment at the LHCAuthor: Cristian Andrei1

1 National Institute of Physics and Nuclear Engineering (IFIN-HH)-


Studies on transverse momentum (pt) distributions, the mean pt values and yield ratios of pions,kaons and protons at mid rapidity (|y|<0.5) for different charged particle multiplicities and eventshapes in pp collisions at √s=7 TeV are reported.The changes in the shape of the pt distribution of pions, kaons and protons as a function of chargedparticle multiplicity and degree of azimuthal isotropy of the considered events are investigated. Themean pt of identified particles, increasing with particle mass, are presented as a function of multiplic-ity and event shape and compared with PYTHIA and PHOJET model predictions. The particle ratiosas a function of pt for high multiplicity and close to azimuthal isotropic class of events are comparedto the minimum bias case. An attempt is also made for extracting an average transverse energydensity and, under several model assumptions, comparing it to the ones of heavy-ion collisions atRHIC and LHC energies.

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Rapidity and centrality dependence of identifiedhadrons inAu+Auand p+p collisions at 200 GeVAuthors: Catalin for BRAHMS Collaboration Ristea1; Oana Ristea1

1 University of Bucharest


TheBRAHMS collaboration hasmeasured identified particles fromAuAu and pp collisions at 200GeVover 3 units of rapidity.

We will investigate the scaling of pion and kaon production with Ncoll and Npart at both centraland forward rapidities.The kaon to pion ratio serves as a measure of equilibration of strange quarks. BRAHMS has foundthat for central collisions the K-/K+ ratio is strongly correlated to the pbar/p ratio. We will showhow this correlation evolves with the centrality of the system.

We will also show the centrality dependence of R_AA(Pt) at both central and forward rapidity forboth mesons and baryons.For central collisions BRAHMS has already shown that R_AA does not depend strongly on rapidity

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but these data represent the first time that the centrality dependence of R_AA has been measured atforward rapidity.

These data thus provide a summary of hadron production over a very wide rapidity and centralityrange.

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Development of the FARICH detector as a possible upgrade forALICE HMPID systemAuthor: Alexeii Kurepin1

Co-authors: Alexander Danilyuk 2; Alexey Onuchin 3; Andrey Reshetin 1; Dmitry Finogeev 4; Evgenij Usenko 1;Evguenij Kravchenko 3; Sergey Kononov 3; Vladimir Razin 1

1 Institute for Nuclear Research (INR)2 Boreskov Institute of Catalysis3 Budker Institute of Nuclear Physics4 nstitute for Nuclear Research (INR


Development of the FARICH detector as a possibleupgrade for ALICE HMPID system

A.B. Kurepin a, A.I. Reshetin a, A.F. Danilyuk c, D.A. Finogeev a,T.L. Karavicheva a, E.V. Karpechev a, V.L. Kirillov c, S.A. Kononov b,E.A. Kravchenko b, A.N. Kurepin a, A.I. Maevskaya a, Yu.V. Musienko a,A.P. Onuchin b, V.I. Razin a, N.S.Topilskaya a, E.A.Usenkoa

a. Institute for Nuclear Research of the Russian Academy of Sciences, 117312 Moscow, Russiab. Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosi-birsk, Russiac. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk,RussiaAbstractAs a possible upgrade of the ALICE experiment the construction of theFocusing Aerogel Ring Imaging Cherenkov (FARICH) detector is proposed.The goal of the FARICH is to extend the working momentum range of the charged particle iden-tification at ALICE for a high transverse momentum PT region up to 10 GeV/c for the pion–kaonseparation and up to 15 GeV/c for kaon–proton separation. It will enable to provide better conditionsfor the investigation of the parton-medium effects at LHC energies.In this report the FARICH detector concept and possible detector construction on the basis of a multi-layer aerogel radiator and photosensitive MRS APD focal plane are presented.The main idea of the FARICH detector development is to employ a Cherenkov radiator composed ofseveral aerogel layers with different index of refraction. Index of refraction of each layer is graduallyincreased along the particle direction, so that Cherenkov ring images produced by different layerscoincide in the focal plane and form more narrow ring image.Simulation was made for a multi-layer radiator based on the Geant4 software toolkit. Results of theFARICH prototype test on the 6 GeV/c negative pion beam of the CERN PS T10 test channel arepresented and discussed.Taking into account the FARICH prototype geometrical efficiency the FARICH Cherenkov angleresolution of about 2,1 mrad was obtained.

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Droplets in the cold and dense chiral phase transition

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Author: Leticia Palhares1

Co-author: Eduardo Fraga 2

1 CEA/Saclay2 IF-UFRJ


The linear sigma model with quarks at very low temperatures provides an effective description forthe thermodynamics of the strong interaction in cold and dense matter, being especially useful atdensities found in compact stars and protoneutron star matter. Using the MSbar one-loop effectivepotential, we compute quantities that are relevant in the process of nucleation of droplets of quarkmatter in this scenario. In particular, we show that the model predicts a surface tension of \Sigma~ 5-15 MeV/fm^2, rendering nucleation of quark matter possible during the early post-bounce stageof core collapse supernovae. Including temperature effects and vacuum logarithmic corrections, wefind a clear competition between these features in characterizing the dynamics of the chiral phaseconversion, so that if the temperature is low enough the consistent inclusion of vacuum correctionscould help preventing the nucleation of quark matter during the collapse process. We also discussthe first interaction corrections that come about at two-loop order.

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Long-Range (Forward-Backward) Pt andMultiplicityCorrelationsin pp Collisions at 0.9 and 7 TeVAuthor: Grigori Feofilov1

Co-author: 2 1 2

1 St. Petersburg State University2 3


Long-Range (Forward-Backward) Pt and Multiplicity Correlationsin pp Collisions at 0.9 and 7 TeVThe ALICE Collaboration

(Submitted by Grigory Feofilov)

Long-range rapidity and azimuthal correlations (LRC) of charged particles are a sensitivetool to study the initial conditions for the Quark Gluon Plasma (QGP) formation [1],[2],[3].Measured in separated pseudorapidity intervals, these correlations, if they exist, mainly Pt-Nch and Pt-Pt, could be the indication in case of pp collisions of processes like color stringfusion[2] or glasma flux tubes formation[3]. The event-by-event analysis of the long-rangeForward-Backward (FB) Nch-Nch, Pt-Nch and Pt-Pt correlations has been performed ondata of the ALICE experiment obtained in the pp runs at 0.9 and 7 TeV pp collision energies.The following observables were defined: Pt (the average transverse momentum in the event)and Nch (the event multiplicity of charged particles). Two pseudorapidity intervals (the“forward” and the “backward” windows) of the variable width from 0.2 to 0.8 rapidity unitswere chosen. Correlations were studied as a function of the width of these windows andon the gap between them, as well as for the different configurations of four pi/2 azimuthalsectors relevant to these windows. Methods for separating the short-range correlations and tomeasure the long-range correlations strength in the limited acceptance of the ALICE centralbarrel (-0.8, 0.8) are discussed. Analysis results show a behaviour compatible with LRCphenomena for these pp collisions. They are compared to PYTHIA and to the model withindependent emitters (strings) [4].

References[1] Abramovskii V. A., Gedalin E. V., Gurvich E. G., Kancheli O. V. , JETP Lett., vol.47,

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337-339 , 1988.[2] M.A.Braun, C.Pajares, Phys.Lett. B287 (1992) 154; Nucl.Phys. B390 (1993) 542;Eur.Phys.J. C16 (2000) 349; N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro,C.Pajares, Phys.Rev.Lett. 73 (1994) 2813; M.A.Braun, C.Pajares, V.V.Vechernin,Phys.Lett. B493 (2000) 54; Internal Note/FMD, ALICE-INT-2001-16, CERN, Geneva(2001) 13p.; M.A.Braun, R.S.Kolevatov, C.Pajares, V.V.Vechernin, Eur.Phys.J. C32(2004) 535; V.V.Vechernin, R.S.Kolevatov, Phys. of Atom.Nucl. 70 (2007) 1797; 1809.[3] L.McLerran, “The Color Glass Condensate and the Glasma”, Proceedings of the Inter-national School of Subnuclear Physics, Subnuclear Series, Vol. 45, 2010.[4] V.V. Vechernin, arXiv:1012.0214, 2010.


Coldnuclearmatter physics at low-x fromd+Au collisions at PHENIX

Author: Mickey Chiu1

1 Brookhaven National Lab


RHIC experiments have observed that inclusive hadron yields inthe forward rapidity (deuteron) direction for √sNN = 200GeV d+Au collisions are suppressed relative to p+p collisions.The mechanism for the suppression has not been firmly established;theoretical descriptions include nuclear shadowing, initial-state parton energy loss, and gluon satu-ration. We present measurements by the PHENIX experiment at RHIC of di-hadron pair productionin d+Aucollisions where the particles in the pair are varied across a widerange of rapidity out to |η| = 3.8 using a new forward electromagnetic calorimeter, the MPC. Thesedi-hadron measurements probe down to parton momentum fractions x ~ 10−3 in the gold nucleus,where the interesting possibility of observing gluon saturation effects at RHIC is the greatest. Ourmeasurements show that the correlated yield of back-to-back pairs in d+Au collisions is suppressedby up to an order of magnitude relative to p+p collisions, and increases with greater nuclear paththickness and with decreasing parton x in the Au nucleus.

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Jets and Underlying Events in p+p Collisions at LHC energies

Author: Andras Gabor Agocs1

Co-authors: Gergely Barnafoldi 1; Peter Levai 1

1 KFKI Research Institute for Particle and Nuclear Physics


Jet matter interaction remains a central question and a theoretical challenge in heavy-ion physicsand might become important in high-multiplicity events inproton-proton collisions at LHC energies. Full jet measurements at LHC are hoped to reconstructthe complete energy loss process and fragmentation of the hardparton in the medium. Since, jet reconstruction will be constrained to small cone sizes, study of theconnection between jets and their underlying event couldprovide a differential tool combined with particle identification in a wide momentum range.

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Charged-particle multiplicity, centrality and the Glauber modelwith ALICE at 2.76 ATeV

Author: Constantinos Loizides1



The measurements of charged-particle multiplicity and transverse energyin Pb-Pb collisions at 2.76 ATeV are reported as a function of centrality. The fraction of inelasticcross section seen by the ALICE detector is estimated using a Glauber model or correcting the databy simulations. The results scaled by the number of participating nucleons are compared with pp col-lisions at the same collision energy and to similar results obtained at the significantly lower energies,and with models based on different mechanisms for particle production in nuclear collisions. Partic-ular emphasis will be given to a discussion on systematic studies of the dependence of the centralitydetermination on the Glauber model, and the validity of the Glauber model at 2.76 TeV.

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Coulomb effects in relativistic heavy ion collisions fromCBM ex-perimentAuthor: Oana Ristea1

1 University of Bucharest, Faculty of Physics


At AGS and SPS energies, the ratio of negative to positive pions at low pion transverse momentareflects the effect of Coulomb repulsion, because the charged particles, especially pions, are highlyinfluenced by the Coulomb field produced by the net charge of the reaction protons. The interactionbetween charged pions and net charged of protons changes the transverse momentum of pions witha Coulomb momentum or Coulomb „kick”.

We will use simulated Au+Au data with HIJING and UrQMD codes, as well as other suited MCmodels, in order to obtain this Coulomb “kick” for the collision systems detected with future CBM(Compressed Baryonic Matter) experiment at FAIR available energies. The predictions for Coulomb“kick” at CBM will be compared with 200 GeV Au+Au results.

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Exact analytic hydrodynamical results and estimations of the ini-tial conditions in p+p and Pb+Pb collisions at LHCAuthor: Márton Nagy1

Co-authors: Máté Csanád 2; Tamás Csörgő 1

1 MTA KFKI RMKI, H-1525 Budapest 114, P.O.Box 49, Hungary2 Dept. Atomic Physics, ELTE University, Budapest, Hungary

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Simple and exact solutions of relativistic hydrodynamics arepresented, including the first exact solution of relativistichydrodynamics with non-zero total angular momentum, an importantcharacteristics of mid-central and peripheral heavy ion collisions.The consequences of these new solutions are explored in dataanalysis. The effects of longitudinal work, acceleration and therotation of the fluid are taken into account in an advanced estimateof the initial energy density, temperature, pressure and the life-timeof the reaction.This advanced estimate of the initial energy density yield values thatare significantly larger in Pb+Pb collisions at LHC energies than the15 GeV/fm**3 initial energy densities obtained from Bjorken’s estimate.

References:M. I. Nagy,http://arxiv.org/abs/0909.4285, Phys. Rev. C (2011) in press

M. I. Nagy, T. Csörgő, M. Csanád,Phys.Rev.C77:024908,2008

T. Csörgő, M. I. Nagy and M. Csanád,J.Phys.G35:104128,2008, Phys.Lett.B663:306-311,2008


Cross section normalization in ALICEAuthor: Ken Oyama1

1 University of Heidelberg


Measurements of reference trigger cross sections were obtained with the ALICE detector, based onbeam properties measured from van der Meer scans where convolution of the beam profiles wereevaluated. The measurement is essential for absolute cross section determination of the physicsprocesses.

Based on this measurement, inelastic cross sections characterizing proton-proton collisions at LHCenergies were obtained with the ALICE detector with a detailed detector Monte-Carlo simulations.As second example, cross sections of reference process, with at least one charged particle is producedin pseudorapidity range of −0.8 < η < 0.8, was measured. These results obtained for

√s=2.76 TeV

and 7 TeV are compared to measurements from other experiments as well as to recent calculationsbased on Regge theories for inelastic cross sections.

The detail descriptions of thees measurements and analysis methods will be presented. The presen-tation will focuses also on instrumental and technical aspects of detectors and accelerators.

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Proposal of new super-compact calorimeter design for the for-ward physicsAuthor: Libor Skoda1

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Co-authors: Jan Cepila 1; Jaroslav Adam 1; Michal Petran 1; Vojtech Petracek 1

1 FNSPE CTU in Prague


Forward rapidity region of the high energy particle collisions affords opportunities for studyingmore details of physics at small Bjorken-x. Measurement of this region within the existing particleexperiments is often restricted due to existing framework and limited space. The aim of our projectis therefore to develop new super-compact ECAL for the forward region based on the tungsten-scintillator calorimeter. The active element of the calorimeter was chosen to be longitudinally ori-ented thin scintillator cards consisting of variable granularity pads with optical readout. Designallows for operation in high multiplicity environment close to y=4.5 and due to its compactness pro-vides also possibility to include HCAL part. Optical readout can operate at high trigger rates andsystem is able to generate L0 trigger.

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Measurement of electrons from heavy-flavor decays in p-p andPb-Pb collisions with the ALICE EMCALAuthor: Shingo Sakai1



High pT heavy flavor (charm and beauty) production is an important probe of partonic energy lossin hot QCD matter.Measurement of the suppression of heavy flavor decay electrons production in nuclear collisionswill reflect the energy loss of the parent heavy quarks.We present the analysis strategy and first results for inclusive heavy flavor decay electrons produc-tion in proton-proton collisions at ¥sqrts = 7 TeV and Pb-Pb collisions at ¥sqrtsNN = 2.76 TeV bythe ALICE experiment, utilizing the large acceptance ALICE Electromagnetic Calorimeter.

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Hadron-Resonance Correlation in pp collisions at the LHC withALICEAuthor: Dilan Madagodahettige Don1


The Width and the mass of short lived resonances are sensitive to the medium properties duringthe phase transition from the deconfined partonic phase to the confined hadronic phase. Heavyhadrons have a larger probability to be produced within the quark gluon plasma phase due to theirshort formation times. Heavy mass, high momentum resonances from jet fragmentation are morelikely to be affected by the chirally symmetric medium, and the identification of the early producedresonances from jet fragmentation might be a viable option to study chirality [1]. Two particle corre-lations in di-jet cones can be used to distinguish between in-medium and in-vacuum fragmentationby assuming that the nearside correlations are surface biased whereas the away-side of a di-jet islikely interacting with the partonic medium.In the analysis a single high pt hadron is chosen as a jet leading particle. Then the correlations of

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phi(1020) and K*(892), identified by their hadronic decay, with this leading particle have been stud-ied in pp collisions at 7 TeV.The characteristics of these resonances (mass and width) as a function ofthe resonance correlation angle have been extracted both on the near side and the away side.

References[1] C. Markert, R.Bellwied, I.Vitev, Phys. Lett B699 92-97

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Di-electron analysis inAu+Au collisions using thePHENIXHadronBlind DetectorAuthor: Ermias T. Atomssa1



The di-electron spectrum is rich with physics signals that assist the characterisation of the mediumcreated in A+A collisions. The measurement, especially at low mass, is however complex due to avery low signal to background ratio. PHENIX has shown in the past that despite this difficulty, it ispossible to learn for example about open charm production [1] or direct photons [2].

The Hadron Blind Detector (HBD) was built, installed and operated by PHENIX with the objective ofreducing the combinatorial background of the di-electron spectrum. This background comes mainlyfrom conversions and Dalitz decay electrons, most significantly, when one leg of the pair was sweptout of the acceptance by the magnetic field, and thus contributes only to the combinatorial back-ground. Currentstatus of the efforts in analyzing the data taken with this detector in Au+Au collisions at 200~GeVwill be shown.

References[1] Phys. Lett. B 670, 313 (2009)[2] Phys. Rev. Lett. 104, 132301 (2010)

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Effect of running coupling on photons from jet - plasma interac-tion in relativistic heavy ion collisionsAuthor: Lusaka Bhattacharya1

1 Saha Institute of Nuclear Physics


We discuss the role of collisional energy loss on high pT photondata measured by PHENIX collaboration by calculating photon yield injet-plasma interaction. The phase space distribution of theparticipating jet is dynamically evolved by solving Fokker-Planckequation. We treat the strong coupling constant (αs) as functionof momentum and temperature while calculating the drag and diffusioncoefficients. It is observed that the quenching factor issubstantially modified as compared to the case when αs istaken as constant. It is shown that the data is reasonably wellreproduced when contributions from all the relevant sources aretaken into account. Predictions at higher beam energies relevantfor LHC experiment have been made.

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608

Nuclearmodification factor in an anisotropicQuark-Gluon-Plasma

Author: Lusaka Bhattacharya1

1 Saha Institute of Nuclear Physics

We calculate the nuclear modification factor (RAA) of lighthadrons by taking into account the initial state momentumanisotropy of the quark gluon plasma (QGP) expected to be formed inrelativistic heavy ion collisions.Such an anisotropy can result from theinitial rapid longitudinal expansion of the matter.A phenomenological model for the space time evolution of theanisotropic QGP is used to obtain the time dependence of theanisotropy parameter ξ and the hard momentum scale, phard.The result is then compared with the PHENIX experimental data toconstrain the isotropization time scale, τiso.It is shown that the extracted value of τiso lies in therange 0.5 ≤ τiso ≤ 1.5.The present calculation is also extended to contrast withthe recent measurement of nuclear modification factor by ALICEcollaboration at

√s = 2.76 TeV. It is argued that similar

values of τiso are closer to the data. The sensitivity ofthe results on the initial conditions has been discussed. We also presentthe nuclear modification factor at LHC energies with

√s = 5.5 TeV.

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Open heavy flavor physics in the muon channel with ALICE inpp collisions at 7 TeV and PbPb at 2.76 TeVAuthor: Xiaoming Zhang1

1 Laboratoire de Physique Corpusculaire, Clermont-Ferrand

Heavy-quark production is one of the probes for the investigation of the propertiesof the high-density medium formed in heavy-ion collisions. This investigation requires also thestudy of proton-proton collisions. Besides providing the necessary baseline for nucleus-nucleuscollisions, proton-proton collisions are of great interest, also in their own right, since they allow totest perturbative QCD at unprecedented low Bjorken-x values. In this contribution, we measure theheavy-flavour production by detecting single muons from semi-leptonic decays.After a description of the ALICE muon spectrometer, we will present the results on theproduction of singlemuons fromheavy flavour decays at forward rapidity (2.5 < y < 4) in pp collisionsat Heavy-quark production is one of the probes for the investigation of the propertiesof the high-density medium formed in heavy-ion collisions. This investigation requiresalso the study of proton-proton collisions. Besides providing the necessary baseline fornucleus-nucleus collisions, proton-proton collisions are of great interest, also in their ownright, since they allow to test perturbative QCD at unprecedented low Bjorken-x values.In this contribution, we measure the heavy-avour production by detecting singlemuons from semi-leptonic decays.After a description of the ALICE muon spectrometer, we will present the results on theproduction of single muons from heavyavour decays at forward rapidity (2:5 < y < 4)in pp collisions at √s = 7 TeV and Pb-Pb collisions at Heavy-quark production is one of the probesfor the investigation of the properties

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of the high-density medium formed in heavy-ion collisions. This investigation requiresalso the study of proton-proton collisions. Besides providing the necessary baseline fornucleus-nucleus collisions, proton-proton collisions are of great interest, also in their ownright, since they allow to test perturbative QCD at unprecedented low Bjorken-x values.In this contribution, we measure the heavy-avour production by detecting singlemuons from semi-leptonic decays.After a description of the ALICE muon spectrometer, we will present the results on theproduction of single muons from heavyavour decays at forward rapidity (2:5 < y < 4)in pp collisions at √s = 7 TeV and Pb-Pb collisions at √sNN = 2.76 TeV. In particular,wewill show the pt-dierential production cross section in pp collisions and compare it to perturbativeQCD predictions, and the nuclear modication factors in Pb-Pb collisions. RAA with respect to a ppreference at √s = 2.76 TeV and RCP in central with respect to peripheral collisions.

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Underlying Event measurement in pp collisions with the ALICEexperiment at LHCAuthor: Sara Vallero1

1 Physikalisches Institut - University of Heidelberg


In a pp collision the jet signature has to be decoupled from the soft or semi-hard bulk of particles origi-nating frombeam-remnant fragmentation, initial and final state radiation andmulti-partonicinteractions:the so-called Underlying Event. Besides being a baseline for jet studies, its characterization providesinsight into the non-perturbative phenomenology in high energy collisions and, in particular, it isa powerful tool to tune Monte Carlo event generators. We studied the underlying activity in twotransverse regions azimuthally perpendicular to the leading track in the event. The relevant observ-ables for this analysis are the multiplicity and sum pT densities of charged particles. We presentthese Underlying Event distributions as measured bythe ALICE collaboration at collision energies of 0.9 and 7 TeV. Three different values of track pTcut-off are considered: 1.0, 0.5 and 0.15 GeV/c. Data are fully corrected to the particle level andcompared to a selection of Monte Carlo models.

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Charged-particle multiplicities in proton–proton collisions at √s= 0.9 TeV, 2.76 TeV and 7 TeV, with ALICE at LHCAuthor: Jean-Pierre Revol1

1 CERN


High-statisticsmeasurementswere performed at LHC,with theALICE central barrel detectors, in thecentral pseudorapidity region (–1 ≤ η < 1) of multiplicity distributions, and pseudorapidity densitiesof primary charged particles produced in proton–proton collisions, at √s = 0.9 TeV, 2.76 TeV and 7TeV.Measurements were obtained for two event classes: inelastic events (INEL) and non-single diffractiveevents (NSD). The data are compared to measurements from other experiments and to simulationswith Monte Carlo event generators PYTHIA and PHOJET.

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Initial condition fluctuations in heavy ion collisionsAuthor: Philippe Mota1

Co-authors: Dirk Rischke 2; Takeshi Kodama 3

1 Institut für Theoretische Physik, Goethe-Universität2 Institute for Theoretical Physics, Goethe University3 Universidade Federal do Rio de Janeiro


We investigate the effect of event-by-event fluctuations and the degree of granularity in the initialconditions on the collective evolution of matter created in heavy-ion collisions using fluid dynamics.Motivated by the glasma-flux-tube scenario, we model the initial condition by a set of randomlydistributed longitudinal tubes in a boost-invariant 2D geometry. The model introduces two param-eters: the number of tubes in each event and the transverse (gaussian) width in energy density of atube. The number of tubes fluctuates event by event and the width of the tubes introduces a gran-ularity to the initial condition. Both parameters strongly affect the hydrodynamical evolution. Forinstance, we observe that the increasing granularity reduces the slope of the transverse momentumspectra, decreases the value of the differential elliptic flow at the average transverse momentum, andgenerates a double-peak structure in the two-particle distribution. With this framework, we aim toconstrain the initial condition of a heavy-ion collision by performing a systematic analysis of theeffects of each parameter on the final observables.

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Detector effects and systematic uncertainties in the directed flowmeasurement with spectator neutrons in ALICE at LHC.Author: Gyulnara Eyyubova1

1 University of Oslo

Directed flow serves as one of the key observable to understand theproperties of the hot and dense matter produced in ion-ion collisions.We report on systematics and detector effects study in the directedflow measurement using the reaction plane estimate provided by thesidewards deflection of neutral spectatorsmeasuredwith the help of ALICE ZeroDegree Calorimeterdetectors.Effects from variation in the beam crossing parameters on the reactionplane resolution are studied via cross correlations between spectatordeflection in the plane transverse to the beam direction.Systematic uncertainties of the measured signal are assessed by comparingresults from different flow measurement techniques, such as the scalar product and the event planemethods.

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The ALICE EMCal Overview and StatusAuthor: Bjorn Nilsen1

1 Creighton University

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An overview of the ALICE EMCal, as installed and operating in 2011, will bepresented. Features of the EMCal construction, acceptance and operation will bedescribed together with details of the calibration and performance of theEMCal. Its newly utilized photon triggering and the yet to be approved Jettriggering will be mentioned along with a list of related physics topics (withdetails given in other presentations).


Characterizing cold nuclearmatter effects through dielectrons ind+Au collisions at √NN = 200 GeV at PHENIXAuthor: Jason Kamin1

1 State University of New York at Stony Brook


Electron-positron pairs are effective probes for investigating thehot, dense matter created in RHIC collisions because they are carry nocolor charge and therefore, once created, do not interact stronglywith the medium. As a result, they retain characteristics of the fulltime evolution and dynamics of the system. Among the many features,the low mass region (m<1 GeV/c2) consists primarily of pairs fromDalitz decays of light hadrons and direct decays of vector mesons thatcan be modified by the medium, while the intermediate (1<m<3GeV/c2) and high (4<m<8 GeV/c2) mass regions are dominatedby pairs from mesons containing charm and bottom respectively.

The PHENIX experiment has presented dielectron continuum spectra forp+p, Cu+Cu and Au+Au collisions at √sNN=200GeV. Anenhancement is observed in Au+Au in the mass range 150<m<750MeV/c2 when compared to the expected hadronic sources scaled fromp+p collisions. In addition, PHENIX has seen an enhancement inCu+Cu collisions in the intermediate mass region, particularly in themost peripheral collisions, making the d+Au reference extremelyinteresting.

Recently PHENIX measured this crucial d+Au reference for heavy ioncollisions. This system not only provides the benefit of identifyingpotential initial state effects contributing to the excesses seen inAu+Au and Cu+Cu but also is a complimentary measurement to the recentsingle electron RdA for open charm. The luminosity collected duringthe 2008 RHIC Run also allows the d+Au measurement to reach out tomass ranges where bottom and Drell-Yan dominate. The analysis of thisdata is in its final stage and the first results will be presented.

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Projectile Spectator Detector for the heavy ion program of theNA61/SHINE experiment at the CERN SPSAuthor: Alexey Kurepin1

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1 Institute for Nuclear Research of Russian Academy of Siences

Study of event-by-event fluctuations as a function of collision energy and size of colliding nucleito search for the critical point of strongly interacting matter is the main goal of the NA61/SHINEexperiment at the CERN SPS. First measurements using secondary beams of light nuclei are plannedat the end of this year. Study of fluctuations requires a good control over fluctuations caused bythe variation of the number of interacting nucleons. In NA61/SHINE this will be achieved by a veryprecise measurements of the number of projectile spectators by the very forward hadron calorimeter,the Projectile Spectator detector, developed and constructed for this experiment. The calorimeterconsists of 44 modules, each of them being a lead/scintillator sandwich with the sampling ratiosatisfying the compensation condition. Light is collected by WLS-fibers embedded in each of 60scintillator plates of the module. The readout is made by 10 micropixel avalanche photodiodes atrear side in each module. Response of the calorimeter prototype measured during beam tests in thewide energy range, 2A-160A GeV, at the hadron and fragmented beams is presented.

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Identified particle flow methods in ALICE at the LHCAuthor: Christian Ivan1

1 GSI


The anisotropic flow of identified particles is an important observable to test the collective behaviorof the dense matter created in heavy-ion collisions.We report on the methods used on the first measurements of elliptic and triangular flow for chargedpions, kaons, protons, neutral kaons and Lambda in lead-lead collisions at sqrt(sNN )=2.76 TeVmeasured with the ALICE detector at the LHC. Scalar product and Q-Cumulant techniques wereused to estimate the flow for charged (neutral) particles in |eta|<0.8 (0.5). The method presented forKs and Lambda can be used for any decaying particle.

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A Design for a Novel TOF Detector with 10 picosecond Resolu-tionAuthor: Mickey Chiu1

1 Brookhaven National Lab


Recent developments in Time of Flight Detector (TOF) technology have made it possible to achievetiming resolutions of close to 10 ps. Much more development needs to be done, particularly inproducing electronicswith picosecond resolutions at reasonable cost. We present recent R&D studiesat Brookhaven National Lab which study the feasibility of building a detector using micro-channelplate detectors and waveform digitizers, over a relatively small area. With such excellent timingresolution, it would be possible to upgrade PHENIX with a TOF detector covering the full azimuthover moderately forward pseudorapities (0.8 < |η| < 1.5), thus increasing the coverage for PID bya factor of 16. We will also present the wealth of new measurements which would be enabled bysuch a new detector for PHENIX.

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Propose of studying the symmetry energy of asymmetric nuclearmatter under super-saturation density at theCooling StorageRingat LanzhouAuthor: Cheng Li1

1 University of Science and Technology of China


Abstract: The Cooling Storage Ring (CSR) at Lanzhou, China is a heavy-ion facility that can acceler-ate nuclei up to 238U with a kinetic projectile energy of several hundred MeV to GeV. By utilizingthe CSR heavy-ion beam on an external target, dense QCD matter can be created. The equation ofstate (EOS) of the strongly coupled matter can be studied via properly chosen physical observables,among which the π-/π+ production ratio probes the symmetry energy of the asymmetrical nuclearmatter at high densities. An External Target Experiment (ETE) is currently proposed for this studybased on first-stage simulation and experimental work. To provide precise measurements and solidconstraint to theory and models, experiment design and systematic requirements must be carefullystudied.

[References]1. W.L. Zhan et al., Nucl. Phys. A 805 (2008) 533c2. X.F. Luo, X. Dong, M. Shao et al., Phys. Rev. C 76, 044902 (2007)3. Bao-An Li, Lie-Wen Chen, Che Ming Ko, Physics Reports 464 (2008) 113–2814. Z.G. Xiao, B.A. Li, L.W. Chen, G.C. Yong, and M. Zhang, Phys. Rev. Lett. 102, 062502 (2009)5. W. Reisdorf et al. (FOPI Collaboration), Nucl. Phys. A 781 (2007) 4596. Z.Q. Feng, G.M. Jin, Int. J. Mod. Phys. E 19 (2010) 16867. W. Trautmann et al., Nucl .Phys. A 834 (2010) 548c

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Azimuthal correlation between photon/π0 and charged hadronswith the ALICE experimentAuthor: Nicolas Arbor1

1 LPSC, UJF Grenoble 1, CNRS/IN2P3, INPG


Measurements of the azimuthal correlation between high momentum photons or π0 and chargedhadrons allow to investigate parton fragmentation following hard collisions, which will providenewinsights on medium effects. We present the experimental analysis which has been applied to the2010 proton-proton collisions at √s = 7 TeV by the ALICE collaboration. The technique is based onthedetection of both neutral particles (photon or π0) using the EMCal electromagnetic calorimeter, andcharged hadrons using the ALICE central tracking system. These proton-proton results should beseenas a reference for heavy ions collisions analysis, and in a broader approach for further gamma-jetstudies.

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Neutral Pionproduction inPbPb collisions at sqrt(s_NN)=2.76TeVmeasured by ALICE via photon conversions

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Author: Daniel Lohner1

1 Ruprecht-Karls-Universitaet Heidelberg


The neutral pion yield is measured with ALICE by reconstructing photonsvia their conversion into e+e- pairs. Transverse momentum spectra arepresented for pp and PbPb collisions as well as the resulting nuclearmodification factor R_AA. The pi0 yield is studied as a function of theemission angle w.r.t. the reaction plane. At high transverse momentumthis provides insights into the path-length dependence of jet-quenching.In addition, the reaction plane dependence of the nuclear modificationfactor R_AA is presented.

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Measurement of pi0 production in p+p collisions at sqrt( s ) = 7TeV with the ALICE EMCalAuthor: Paraskevi Ganoti1

1 Oak Ridge National Laboratory


Themeasured π0 production spectrum in p+p collisions at 7 TeV (2010 data), where both photons arereconstructed in the ALICE EMCal, will be presented. An accurate measurement of the π 0 produc-tion spectrum requires a thorough understanding of the response of the ALICE EMCal. The detailsof the analysis aredescribed, including comparisons with Monte Carlo simulations of the EMCal response, in termsof energy non-linearity and resolution, as measured in test beam data. The effect of photon con-versions in the material in front of the EMCal in ALICE on the pT dependence of the π 0 massand the π 0 reconstruction efficiency will also be discussed. The various fundamental correctionsand associated systematic errors, as determined by Monte Carlo simulations will be described andsummarized.

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Studies of ω(782)→π0γ→3γ in p+p collisions at √s = 7 TeVwiththe ALICE electromagnetic calorimetersAuthor: Renzhuo Wan1

1 IOPP-CCNU, Wuhan, China and IPHC-UDS, Strasbourg, France


ALICE electromagnetic calorimeters, PHOS (PHOton Spectrometer) and EMCAL (ElectroMagneticCALorimeter), have the capability to detect and identify photons over a large pT range. The mea-surement of vector meson ω(782) to π0 γ channel thanks to the calorimeters is interesting both as atest of pQCD and as a probe to explore the properties of hot-dense matter created in heavy-ion colli-sions. Two complementary analysis techniques are explored: one is only based on the three photoninvariant mass, while the other takes profit of the cluster shower shapes to constrain the analysis.Here we show the expected pT reach with these techniques. Prospects on the measurement of π0 γinvariant mass studies in pp collisions at √s = 7 TeV will also be presented.

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Measurement of eta meson production in pp collisions at √s = 7TeV with the ALICE electromagnetic calorimeterAuthor: Olga Driga1

1 Laboratoire de Physique Subatomique et des Technologies Associees, SUBATECH


The measurement of the neutral meson transverse momentum (p_T) spectra in the new energyregime of the LHC is an important input to constrain theoretical models describing hadron pro-duction within the perturbative quantum chromodynamics. Such measurements are the first onesthat have been performed by the ALICE electromagnetic calorimeter (EMCal) in proton-proton colli-sions at sqrt(s)=900 GeV, 2.76 TeV and 7 TeV over a wide transverse momentum range at mid-rapidity|y|<0.7.The complete chain of the neutral meson analysis which includes data quality assessment, data cor-rection and Monte Carlo tuning, reconstruction of the raw eta p_T spectrum from invariant massanalysis and efficiency calculations will be presented. Special emphasis on systematic uncertaintyevaluation will be made. The direct comparison of the p_T spectra obtained by EMCal, with com-plimentary measurements by other ALICE detectors allows independent cross-checks of the EMCalresults and provides a first test bench for the pQCD predictions at LHC energies in a wide kinematicrange. The measured ratio of eta meson and pi0 production will be presented and compared withresults obtained at lower energies.

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pi0 and eta meson production in pp collisions at 0.9, 2.76 and 7TeV measured with ALICE PHOSAuthor: Yuri Kharlov1

1 IHEP


The Photon Spectrometer of the ALICE experiment, PHOS, has performed extensive measurementsof neutral meson production in proton-proton collisions at the energies of 0.9, 2.76 and 7 TeV. Inclu-sive spectra of pi0 and eta mesons were measured in mid-rapidity in a wide transverse momentumrange. Dependence of the pi0 spectrum on event multiplicity has been also studied. Comparisonwith pQCD calculations allows to constrain the model parameters. Phenomenology of pi0 produc-tion versus collision energy will be discussed. Perspectives on the neutral meson measurements inpp collisions at high pT will be demonstrated.

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Correlation Between Mean pT and Charged Particle Multiplicityin pp Collisions at √s = 0.9, 2.76 and 7 TeV with ALICEAuthor: Philipp Luettig1

1 CERN


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The study of transverse momentum distributions of charged particles in pp collisions at the LHCprovides information about both soft and hard contributions to particle production. Charged parti-cle transverse momentum distributions in pp collisions at 0.9, 2.76 and 7 TeV have been measuredat mid-rapidity (|eta|< 0.8) by ALICE. We present the energy dependence of the inclusive averagetransverse momentum <pT> and the correlation between <pT> and the charged particle multi-plicity. The results are compared to simulations with Monte Carlo event generators. In this poster,details of the extrapolation to pT = 0 as well as the procedure to correct the measured multiplicity toa true multiplicity are presented. Moreover, possible energy-independent scaling properties of thecorrelation between <pT> and multiplicity are discussed.

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Energy density in Pb-Pb Collisions at LHCAuthor: Oeystein Djuvsland1

1 University of Bergen


In ultra-relativistic heavy ion collisions at sufficiently large energy densities, a new state of stronglyinteracting matter is created, often referred to as the Quark Gluon Plasma (QGP).The produced medium can be attributed a formation time, and a formed energy density can be esti-mated based on the transverse energy (ET ) produced in these collisions via the Bjorkenformula (Bjorken, 1983).

Data from Pb-Pb collisions at sqrts_NN=2.76 TeVmeasured with the ALICE experiment in 2010 hasbeen analyzed to extract dE_T/d_eta for different centrality bins. The measurement has been donewith two methods, using the tracking system to obtain the hadronic part and calorimetry for theelectromagnetic part of E_T. We will present the status of the measurements, with the main focuson the calorimetry measurement with the ALICE PHOS. Due to its high energy resolution PHOS iswell suited for precision measurements starting at low gamma energies.

We will also compare to the available theoretical models, which display a rather large variation intheir predictions. Results from earlier experiments up to RHIC energies are consistent with alinear increase in E_T with ln(sqrts). Gluon saturation models, which reproduce the charged par-ticle multiplicity well, generally predict a much stronger increase in E_T towards the energies atLHC. The prospects for using E_T measurements to discriminate between theoretical models will bediscussed.

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Transverse energy measurements with ALICE in pp and Pb-PbcollisionsAuthor: Christine Nattrass1

1 University of Tennessee/Knoxville


The ALICE detector allows precise measurements of the transverse energy in p+p and Pb-Pb colli-sions at LHC energies. We will discuss studies of the transverse energy in p+p collisions at sqrts =0.9, 2.76, and 7 TeV and in Pb-Pb collisions at sqrts_NN = 2.76 TeV.

The ALICE Inner Tracking System (ITS) and the Time Projection Chamber (TPC) are used for precisemeasurements of the transverse energy of charged hadrons and the electromagnetic calorimeters

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(PHOS and EMCal) are used for measurements of the transverse energy for electrons, photons, andneutral hadrons which dominantly decay through Dalitz decays.

The detector performance will be presented and the measurement technique described in detail.Particular focus will be placed on the hadronic E_T and EMCal measurements, and also on studieswith Monte Carlo simulations and assignment of systematic errors for the analyses.

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Ridge Studies in Pb-Pb Collisions at the LHC based on Numberand Transverse Momentum Two-Particle Correlation Functions

Author: Claude Andre Pruneau1



Observations of a ridge on the near-side, and a dip on the away-side of two-particle correlationsmeasured in central Au + Au collisions have generated considerable interest at RHIC. Are the twophenomena connected? Do they result from jet interactions with the medium, or do they naturallyarise from the rapid thermalization and hydrodynamic expansion of collision systemssubject to large initial fluctuations? We present measurements, carried with the ALICE detector, ofnumber (R2 ) and transverse momentum (∆pt ∆pt ) correlation functions in Pb + Pb collisions. Thetwo correlation functions are studied as a function of collision centrality for ++, - -, and +- chargedparticle pairs in various momentum ranges. The like-sign and unlike-signcorrelations exhibit a different evolution with collision centrality. We combine these correlations tostudy charge dependent (CD) and charge independent (CI) correlation functions. We characterizethese distributions by studying Fourier decompositions of ∆φ projections of the R2 and ∆pt ∆ptcorrelation functions for different ranges of ∆η. Of particular interest are the evolutionof the ratios of 3rd, and 4th harmonics to the 2nd harmonics with number of participants. We willdiscuss these results in light of a MC Glauber model of the initial eccentricity of collision nucleonparticipants.

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Three-Particle Jet-LikeCorrelations inPb-PbCollsions at sqrt(s_NN)=2.76TeV at ALICEAuthor: Jason Glyndwr Ulery1

1 Johann-Wolfgang-Goethe Univ.


Two-particle correlations at RHIC and SPS in heavy-ion collisions have shown away-side structuresthat could be explained by conical emission, either fromMach-cone shock waves or Cerenkov gluonradiation, or other physics mechanisms such as path-length dependentenergy loss or deflection by radial flow. Three-particle correlations at RHIC showed evidence ofconical emission. More recently, triangular flow has been suggested to be present in heavy-ion collisions; it was assumed to be zero in the RHIC and SPS analayses. Triangular flow has alsobeen suggested as a possible source of the structure seen in the correlations at RHIC and SPCs. Westudy 3-particle correlations at ALICE to look for the presence of conical emission at LHC energies.Backgrounds in this study will include the contributions from the 2nd, 3rd and 4th harmonics offlow. This poster will show the analysis and the resultsobtained from 2.76 TeV Pb-Pb collision data by the ALICE experiment at the LHC.

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Prompt and detached J/psi production in p–p collisions at Sqrt(s)= 7 TeV with the ALICE detectorAuthor: Carmelo Di Giglio1

1 Universita’ di Bari and INFN sezione di Bari


We will discuss the ALICE measurement preparation of the fraction of detached J/ψ (detected via itsdi-electron decay) coming from beauty hadrons semi-inclusive decays, i.e B → J/ψ + X.The measurement relies on the combined use of the ALICE TPC for tracking and particle identifi-cation via dE/dx, the ITS for tracking and detection of displaced vertices and the TRD for particleidentification.Shown results are based on data collected in 2010 in proton-proton collisions at √s = 7 TeV.With increasing statistics following ALICE forthcoming data–taking, the approach adopted will bealso crucial for both extracting the prompt J/ψ contribution from the total J/ψ cross–section, andmeasuring the differential beauty production cross-section, down to very low transverse momen-tum.

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Production of Neutral Mesons Identified by ALICE-PHOS in Pb-Pb collisions at sqrts_NN=2.76TeVAuthor: Hisayuki Torii1



The finely segmented structure and small Moliere radius of the ALICE-PHOS detector allows toseparate two photons from a pi^0 decay at pT=30 GeV/c with an efficiency of about 100%; at evenhigher pT with smaller efficiency.

In this poster, we will present the pi0 production yield measurement with the ALICE-PHOS detectorin various centralities in Pb+Pb collisions at sqrts_NN=2.76TeV. By comparing the productionyield in peripheral collisions to that in pp collisions, we will discuss possible cold nuclear mattereffects. The RAA and RCP ratio of pi0 will be presented to be compared with previous results at SPSand RHIC.

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R&D on MRPC for STAR MTDAuthor: Yongjie Sun1

1 Dept. of Modern Physics, University of Science and Technology of China


A Muon Telescope Detector (MTD) is proposed for the upgrade of the STAR (the Solenoidal TrackerAt theRHIC) experiment at RHIC. By the measurement of muons of a few GeV/c, the MTD will allow thedetection of

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di-muon pairs fromQuarkGluon Plasma (QGP) thermal radiation, quarkonia, and light vectormesons.Thecorrelation of quarks and gluons as QGP resonances, Drell-Yan production, and the measurement ofheavy flavorhadrons via semi-leptonic decays into single muons are also possible. These measurements will ad-vance ourknowledge of the nuclear matter formed in the relativistic heavy ion collisions at RHIC.MRPC (Multi-gap Resistive Plate Chamber) with long-strip readout will be used as the detector forthe MTDwith its excellent performance and relatively low cost per channel. This first prototype of LMRPC(Long-stripMRPC) has 10 gas gaps of 250 μm and the signal is read out by six 90 cm long strips of 2.5 cm wide.The testperformance with both cosmic ray and test beam shows that the time resolution is around 70 ps, thedetectionefficiency is higher than 95% and the spatial resolution along strips is less than 1 cm. The “real size”prototypehas 6 gaps of 250 μm and the readout strips are 3.8 cm wide. The cosmic ray test shows the efficiencyis higherthan 90% and time resolution around 90 ps which is good enough for the MTD requirements. Boththe firstprototype and “real size” detectors have been installed in STAR and taken data successfully. Themass productionof the LMRPC will start soon in this year.


Femtoscopy of PbPb and pp collisions at the LHCwith the ALICEexperiment


We report on the results of femtoscopic analysis of Pb-Pb collisions at√sNN = 2.76~TeV with iden-tical pions and pp collisions at

√s = 0.9, 2.76 and 7~TeV with identical pions and kaons.

Detailed femtoscopy studies in heavy-ion collisions at SPS and RHIC have shown that emissionregion sizes (”HBT radii”) decrease with increasing pair momentum, which is understood as a man-ifestation of the collective behavior of matter. The trend was predicted to persist at the LHC. Thedata from Pb-Pb collisions confirm the existence of a flowing medium and provide strict constraintson the dynamical models. Similar analysis is carried out for pp collisions for pions and kaons andqualitative similarities to heavy-ion data are seen, especially in collisions producing large numberof particles. The observed trends give insight into the soft particle production mechanism in pp col-lisions.3D radii were also found to universally scale with event multiplicity in heavy-ion collisions. Weextend the range of multiplicities both upwards with the Pb-Pb data and downwards with the ppdata to test the scaling in new areas. In particular the high multiplicity pp collisions reach particledensities comparable to the ones measured in peripheral Cu-Cu and Au-Au collisions at RHIC. Thisallows for the first time to directly compare freeze-out sizes for systems with very different initialstates.


Flow - Theory perspective


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Fluctuations & correlations – TH perspective



Results from correlation studies in ALICE


The talk presents results from hadron correlations in PbPb collisions at 2.76 TeV with ALICE. Un-triggered di-hadron correlations studies are shown which provide a map of the bulk correlationstructures in heavy-ion collisions. The long-range correlation region is further studied by triggeredcorrelations which addresses the dependence on trigger and associated pT. The measured correla-tion functions are decomposed with a multi-parameter fit and into Fourier components. The jetyield modification factor I_AA extracted using triggered correlations is presented.

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Jet yield enhancement in high-tower trigger events with the AL-ICE Electromagnetic CalorimeterAuthor: Rongrong Ma1

1 Yale University

The ALICE detector carries out comprehensive measurements of high energy nucleus-nucleus colli-sions. Jet reconstruction in ALICE is enabled by combining charged particle measurements in thecentral tracking system, and neutral particle measurements in the Electromagnetic Calorimeter (EM-Cal). In this poster, wewill show the jet yield enhancement using the EMCal high-tower (HT) trigger,compared to minimum bias (MB) trigger, taken in p+p collisions at \sqrts=2.76TeV in 2011. Compar-ison of the two spectra enables determination of the gain in statistics and assessment of HT triggerbias. This work will lead to a measurement of the inclusive differential jet cross-section.


STAR correlations and fluctuations


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Common discussion with 4 speakersCorresponding Author: [email protected]

Closing / 646

Presentation of QM12Corresponding Author: [email protected]

Closing / 647

Closing

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ALICE vertexing performance and charm reconstructionAuthor: Xianbao Yuan1

1 University and INFN, Padova, Italy - Institute of Particle Physics, Central China Normal University

ALICE is a general-purpose heavy-ion experiment designed to studythe physics of strongly interacting matter and the quark gluon-plasma in nucleus-nucleus collisionsat the LHC.The measurement of open charm and open beauty production allowsone to investigate the mechanisms of heavy-quark production,propagation and, at low momenta, hadronisation in the hot and densemedium formed in high-energy nucleus-nucleus collisions.The track impact parameter, defined as the distance of closestapproach of a track to the primary(collision or initial) vertex, is the variable allowing to evaluatethe displacement of the track. It is a critical variable for the selection of physics signals which aretagged by the secondary vertex with a small displacement from the primary vertex.This is, in particular, the case for the detection of particles with open charm and open beauty, namelyD0 (cτ ∼ 123μm) , D+ (cτ ∼ 315μm) and B mesons(cτ ∼ 500μm). The main requirement applied for theselection of such particles is the presence of one or more daughter tracks (decay products) whichare displaced from the primary vertex (e.g. for D0 → K− π+ two displaced tracks are required.This poster presents the ALICE track impact parameter resolutionfor the pp and Pb-Pb collisions, as well as the performance on theexclusive reconstruction of the decay D0 → K− π+.

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Preparation for open charmelliptic flowmeasurement viaD-mesondecay to hadrons with ALICEAuthor: Robert Grajcarek1

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1 University of Heidelberg, Heidelberg, Germany


A Large Ion Collider Experiment (ALICE) at the Large Hadron Collider (LHC) has been built inorder to identify and characterize the quark gluon plasma (QGP) in high-energy nuclear collisions.As charm quarks are produced at the early stage of the collision, theyserve as ideal probes for a QGP. The ALICE detector with its powerful capabilities such as particleidentification, vertexing at sub-millimeter precision and tracking in a high multiplicity environmentaddresses the charm sector in nuclear collisions. It is still an open question whether charm quarkstake part in the collective motion of the expanding fireball in ultrarelativistic heavy ion collisions.The determination of the anisotropy parameter v2 of the D-mesons D+, D0 and D∗+ will provide adecisive answer.We report on the current status of the development of the tools for the D-meson v2-measurement atALICE for the three charmed mesons in various hadronic decay channels.We will show performance plots obtained with these tools from the 2010 lead-lead run at √s_NN =2.76 TeV and will give an outlook for the upcoming high statistics lead-lead run at the end of thisyear.

650

Probing the gluonic structure of matter at a future Electron-IonCollider

The probing of nuclei and nucleons via deep-inelastic and diffractive processes in the high-energy(low-x) regime will open a new precision window for the investigation of the gluonic structure ofmatter.

Studies of e+p collisions at HERA and especially d+Au collisions at RHIC have found tantalizinghints of saturated gluon densities, a phenomenon with substantial impact on the physics of heavy-ion collisions. Unveiling the collective behavior of densely packed gluons under conditions wheretheir self-interactions dominate will require an Electron-Ion Collider (EIC): a new facility with capa-bilities well beyond those of any existing accelerator. Such a collider could be sited either at BNL orJLAB.

In my talk I will outline the compelling physics case for e+A collisions with a focus on the oppor-tunities for small-x physics. I will discuss the related key measurements and give a brief status ofmachine concepts, detector design, and timeline.

651

eA collisions at the Large Hadron-electron Collider

I will show the possibilities for electron-ion studies offered by the proposed electron-hadron col-lider at CERN, the Large Hadron-electron Collider [1]. After a short introduction on open problemsat small x, I will briefly present the machine and detector. Then I will focus on small-x aspects inelectron-nucleus collisions, first on inclusive measurements and the determination of nuclear par-ton densities, and then on diffraction. I will finish by discussing some opportunities for final statestudies.

[1] M. Klein et al., Prospects for a Large Hadron Electron Collider (LHeC) at the LHC, EPAC’08,11th European Parti cle Accelerator Conference, 23- 27 June 2008, Genoa, Italy; http://cern.ch/lhec.

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Proposal for QM13/14 in Japan


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Preparation of QM2012 at Washington


IAC / 654

Proposal for QM13/14 in Darmstadt



Leptonic observables in sqrt(s_NN)=2.76 TeVPbPb collisionsmea-sured with the ATLAS detector at the LHC


A broad program of measurements using heavy ion collisions is underway in ATLAS, with the aimof studying the properties of QCD matter at high temperatures and densities. Leptonic observablesare essential tools for the study of heavy ion collisions since leptons do not interact strongly andthus pass through the strongly-coupled medium unaffected. The centrality dependence of J/psi andZ yields, observed through their di-muon channel, are important measurements both for assessingmodifications of particle production as well as probing particular regions of the nuclear PDFs. Wboson measurements are also possible using single leptons, and provide another handle on the initialstate.This talk describes measurements performed using up to 9 µb-1 of lead-lead collision data providedat a nucleon-nucleon center-of-mass energy of 2.76 GeV by the Large Hadron Collider and collectedby the ATLAS Detector during November and December 2010

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Proposal for QM13/14 in Bologna


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Charged-particle multiplicities in proton–proton collisions at √s= 0.9 TeV and 7 TeV, with the ALICE Forward Multiplicity Detec-tor at LHC


659

Charged pion spectra at high pT measured via dE/dx with the AL-ICE TPCAuthor: Peter Christiansen1

1 Lund University


The TPC is the main tracking detector in the central barrel (|η| ≤ 1) of the ALICE experiment. In ad-dition to tracking it provides particle identification through the measurement of the specific energyloss, dE/dx, which depends only on βγ = p/m. At low momentum, p<1GeV/c, pions, kaons, andprotons, can be cleanly separated in different momentum intervals. At high momentum, p>3GeV/c,the yield of pions, kaons, and protons can be extracted statistically on the relativistic rise.In this poster I will show results from pp @ 2.76 TeV and Pb-Pb @ 2.76 TeV/nucleon for 3.0<pT<20.0for charged pions. By combining the results from this analysis with results from the analysis ofunidentified charged particles, the charged pion spectra and the charged pion RAA is determined.

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Charged pion spectra at high pT measured via dE/dx with the AL-ICE TPCAuthor: Peter Christiansen1

1 Lund University

The TPC is the main tracking detector in the central barrel (|η| ≤ 1) of the ALICE experiment. In ad-dition to tracking it provides particle identification through the measurement of the specific energyloss, dE/dx, which depends only on βγ = p/m. At low momentum, p<1GeV/c, pions, kaons, andprotons, can be cleanly separated in different momentum intervals. At high momentum, p>3GeV/c,the yield of pions, kaons, and protons can be extracted statistically on the relativistic rise.

In this poster I will show results from pp @ 2.76 TeV and Pb-Pb @ 2.76 TeV/nucleon for 3.0<pT<20.0for charged pions. By combining the results from this analysis with results from the analysis ofunidentified charged particles, the charged pion spectra and the charged pion RAA is determined.

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Proposal for a QM in Brazil


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QM2011

Flash talks / 663

First B→J/ψmeasurement in PbPb collisions at 2.76 TeVwith theCMS detector


Flash talks / 664

First measurement of Upsilon suppression

665

pendingAuthor: Yvonne Pachmayer1

1 Univ. Heidelberg


Flash talks / 666

Measurement of theNuclearModification Factor of Electrons fromHeavy Flavour Decays atMid-Rapidity in Pb-Pb Collisions at 2.76TeV with ALICE


Flash talks / 667

Probingnuclear partondensities andparton energy loss processesthrough photon + heavy-quark jet production in p-A and A-A col-lisions

Flash talks / 668

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Dimuon radiation at the CERN SPS within a hybrid evolutionmodelCorresponding Author: [email protected]

Flash talks / 669

Local Parity Violation or Local Charge Conservation/Flow?Corresponding Author: [email protected]

Flash talks / 670

Production of (anti)nuclei in pp and PbPb collisions with ALICEat the LHCCorresponding Author: [email protected]

Flash talks / 671

Continuous Time Monte Carlo for QCD in the Strong CouplingLimitCorresponding Author: [email protected]

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book of abstracts - cern indico

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