beam energy scan program at rhic

1

Beam Energy Scan Program at RHIC Michal Šumbera

Nuclear Physics Institute AS CR, Řež/Prague

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World’s (second) largest operational heavy-ion colliderWorld’s largest polarized proton collider

RHIC BRAHMSPHOBOSPHENIX

STAR

AGS

TANDEMS

Relativistic Heavy Ion ColliderBrookhaven National Laboratory (BNL), Upton, NY

Animation M. Lisa

Year System sNN [GeV]

2000 Au+Au 130

2001 Au+Au 200

2002 p+p 200

2003 d+Au 200

2004 Au+Aup+p

200, 62.4200

2005 Cu+Cu 200, 62.4, 22

2006 p+p 62.4, 200, 500

2007 Au+Au 200

2008d+Aup+p

Au+Au

2002009.2

2009 p+p 200, 500

2010 Au+Au 200, 62.4, 39, 11.5, 7.7

2011 Au+Aup+p

200,19.6,27500

2012 U+UCu+Au

p+p

193200

200,510

3

Recorded Datasets

Fast DAQ + Electron Based Ion Source + 3D Stochastic cooling

4

– Perfect liquid BRAHMS, PHENIX, PHOBOS, STAR, Nuclear Physics A757 (2005)1-283

– Number of constituent quark scaling PHENIX, PRL 91(2003)072301; STAR, PR C70(2005) 014904

– Jet quenching PHENIX, PRL 88(2002)022301; STAR, PRL 90(2003) 082302

– Heavy-quark suppression PHENIX, PRL 98(2007)172301, STAR, PRL 98(2007)192301

– Production of exotic systems• Discovery on anti-strange nucleus STAR, Science 328 (2010) 58

• Observation of anti-4He nucleus STAR, Nature 473 (2011) 353

– Indications of gluon saturation at small x STAR, PRL 90(2003) 082302; BRAHMS, PRL 91(2003) 072305; PHENIX ibid 072303

Remarkable discoveries at RHIC

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Introducing sQGP …

1st/2nd order

QCD Phase Diagram

Crossover

Particle Physics

~21012K

6

7

… and how was it discovered

<Nbinary>/sinelp+p

Nucleus-nucleus yield

AA hadronsleadingparticle suppressed

q

q

?

NULL Result

If R = 1 here, nothing “new” is going on

Scaling AA to pp (or central to peripheral)

8

FERMILAB-Pub-82/59-

THY

Phys.Lett.B243(1990)432

Au + Au Experiment d + Au Control Experiment

• Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control experiment.

New state of matter is produced in central Au+Au collisions at √sNN=200GeV

Suppresion of leading hadrons at RHIC

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…and at LHC …

ALICE, Phys.Lett. B696 (2011)30

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…and compared to pA reference

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arXiv:1210.4520v1

http://arxiv.org/abs/1210.4520

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Single hadron RAA: RHIC vs LHC

RAA

RAA for both systems looks similar

LHC: Suppression of inclusive jets

13Like for charged particles, high-pT jet RAA flat at ≈ 0.5

Fully unfolded inclusive jet RAA pp 2.76 TeV reference

CMS-PAS HIN-12-004

Dihadron azimuthal correlations at RHIC

Azimuthal distribution of hadrons with pT > 2 GeV/c relative to trigger hadron with pT

trig > 4 GeV/c (background subtracted). Data are from p+p, central d+Au and central Au+Au collisions.

STAR, PRL 90(2003) 082302

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Photon tag:• Identifies jet as u,d quark jet• Provides initial quark direction• Provides initial quark pT

Jet (98 GeV)

Photon(191GeV)

… and g+jet at LHC

1515

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Energy Dependence of Elliptic Flow

ALICE: PRL 105 (2010) 252302

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v2(pT): LHC vs. RHIC

The same flow properties from √sNN=200 GeV to 2.76 TeV

ALICE: PRL 105 (2010) 252302

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1) QuenchingAll hard hadronic process are strongly quenched 2) FlowPanta rhei: All soft particles emerge from the common flow field

The ‘Standard Model’ of high energy heavy ion collisions

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0) Turn-off of sQGP signatures

1) Search for the signals of phase boundary 2) Search for the QCD critical point

Why to go to lower energies?

QGP Turn-offCritical Point

First

Order

First Order

Phase Transition

Cross-Over

The RHIC Beam Energy Scan Project• Since the original design of RHIC (1985), running at lower energies has been envisioned.

• Possibilities of RHIC running at lower energies were studied with a series of test runs: 19.6 GeV Au+Au in 2001, 22.4 GeV Cu+Cu in 2005, and 9.2 GeV Au+Au in 2008.

• In 2009 the RHIC PAC approved a proposal to run a series of six energies to search for the critical point and the onset of deconfinement.

• These energies were run during the 2010 and 2011 running periods.

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Selected Results

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(0-5

%/6

0-80

%)

STAR Preliminary

Suppression of Charged Hadrons …

PRL 91, 172302 (2003)

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(0-5

%/6

0-80

%)

STAR Preliminary

… and its Disappearance

RCP ≥ 1 at √sNN ≤ 27 GeV - Cronin effect?

PRL 91, 172302 (2003)

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STAR Preliminary

RCP : Identified Particles

RCP (K0s) < 1 @ √sNN > 19.6 GeV

RCP > 1 @ √sNN ≤ 11.5 GeV For pT > 2 GeV/c:

• Baryon-meson splitting reduces and disappears with decreasing energy

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W/f ratio falls off at 11.5 GeV

STAR Preliminary

Baryon/Meson Ratio

v1(y) is sensitive to baryon transport, space - momentum correlations and QGP formation

Azimuthal Anisothropy

1

1 2 cos ( )n nn

dN v nd

Generated already during the nuclear passage time

(2R/g≈.1 fm/c@200GeV)

⇒ It probes the onset of bulk collective dynamics during thermalization

Directed flow is quantified by the first harmonic:

rapidity

<px> or directed flow

Directed flow is due to the sideward motion of the particles within the reaction plane.

(preequilibrium)26

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STAR Preliminary

v 1Directed Flow of p and π

Mid-central collisions:Pion v1 slope: Always negative (7.7-39 GeV)(Net)-proton v1 slope: changes sign between 7.7 and 11.5 GeV - may be due to the contribution from the transported protons coming to midrapidity at the lower beam energies

p π

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Energy Dependence of v2

• The rate of increase with collision energy is slower from 7.7 to 39 GeV compared to that between 3 to 7.7 GeV

ALICE: PRL 105, 252302 (2010)PHENIX: PRL 98, 162301 (2007) PHOBOS: PRL 98, 242302 (2007) CERES: Nucl. Phys. A 698, 253c (2002).E877: Nucl. Phys. A 638, 3c(1998). E895: PRL 83, 1295 (1999). STAR 130 Gev:

Phys.Rev. C66,034904 (2002).STAR 200 GeV:

Phys.Rev. C72,014904 (2005).

STAR Preliminary

STAR, ALICE: v2{4} resultsCentrality: 20-30%

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v2(pT): First Result

STAR: Nucl.Phys. A862-863(2011)125

v2 (7.7 GeV) < v2 (11.5 GeV) < v2 (39 GeV) v2 (39 GeV) ≈ v2 (62.4 GeV) ≈ v2 (200 GeV) ≈ v2 (2.76 TeV)

⇒ sQGP from 39 GeV to 2.76 TeV

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v2(pT): Final ResultSTAR Coll.: e-Print arXiv:1206.5528

For pT < 2 GeV/c: v2 values rise with increasing √sNN For pT ≥ 2 GeV/c: v2 values are (within stat. errors) comparableThe increase of v2 with √sNN,could be due to change of chemical composition and/or larger collectivity at higher collision energy.

ALICE data: PRL 105, 252302 (2010)

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Corresponding anti-particlesParticles

v2 vs. mT-m0

Baryon–meson splitting is observed when collisions energy ≥ 19.6 GeV for both particles and the corresponding anti-particles For anti-particles the splitting is almost gone within errors at 11.5 GeV

STAR Preliminary

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Particles vs. Anti-particles Beam energy ≥ 39 GeV• Δv2 for baryon and anti-baryon within 10%• Almost no difference for mesons Beam energy < 39 GeV• The difference of baryon and

anti-baryon v2

→ Increasing with decrease of beam energy

At √sNN = 7.7 - 19.6 GeV • v2(K+)>v2(K-) • v2(π-) >v2(π+) Possible explanation(s)• Baryon transport to midrapidity?

ref: J. Dunlop et al., PRC 84, 044914 (2011)• Hadronic potential? ref: J. Xu et al., PRC 85, 041901 (2012)

The difference between particles and anti-particles is observed

STAR Preliminary

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Universal trend for most of particles – ncq scaling not broken at low energies ϕ meson v2 deviates from other particles in Au+Au@(11.5 & 7.7) GeV: ~ 2σ at the highest pT data point

Reduction of v2 for ϕ meson and absence of ncq scaling during the evolution the system remains in the hadronic phase [B. Mohanty and N. Xu: J. Phys. G 36, 064022(2009)]

NCQ Scaling Test

Particles STAR Preliminary

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Accessing Phase Diagram

T-mB:From spectra and ratios

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p, K, p Spectra

STAR Preliminary

Slopes: p > K > p. Proton spectra: without feed-down correctionp,K,p yields within measured pT ranges: 70-80% of total yields

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STAR PreliminarySTAR Preliminary

Strange Hadron SpectraX

Au+Au 39 GeVAu+Au 39 GeV

K0s L

Au+Au 39 GeV

f, K0s: Levy function fit

L, X : Boltzmann fit L: feed-down corrected

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STAR Preliminary

Chemical Freeze-out Parameters

Centrality dependence of freeze-out temperature with baryon chemical potential observed for first time at lower energies

THERMUS* Model:Tch and mB

Particles used: p, K, p, L, K0

s, X

S. Wheaton & J.Cleymans, Comp. Phys. Com. 180: 84, 2009.

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STAR Preliminary

Au+Au

Kinetic Freeze-out Parameters

Higher kinetic temperature corresponds to lower value of average flow velocity and vice-versa

Blast Wave: Tkin and <b>

Particles used: p,K,p

STAR Preliminary

1. Turn-off of QGP signatures:• NCQ breaks down below 19.6 GeV• High pt suppression not seen below 19.6 GeV• LPV effect not seen below 11.5 GeV

2. Evidence of the first order phase transition.• v1 sign change above 7.7• Inflection in v2 and dET/dh at 7.7 • Azimuthal HBT signal inconclusive

3. Search for the critical point. • K/p, K/p, or p/p fluctuations are not conclusive.• Higher moments of the proton distributions

Overview of the BES I Results

Clear

Evidence

StrongHints

Hints

Daniel Cebra @ APS DNP Meeting – Town MeetingNewport Beach, CA, 10/26/2012

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Beam Energy Scan Phase- II

Beam Energy Scan II

BES II

•BES II will focus on the most interesting regions of the phase diagram

•Electron cooling is key to the feasibility of this program; without cooling, BES II would take ~70 weeks

√SNN (GeV) 62.4 39 27 19.6 15 11.5 7.7

mB (GeV) 70 115 155 205 250 315 420

BES I (MEvts) 67 130 70 36 --- 11.7 4.3

Rate(MEvts/day) 20 20 9 3.6 1.6 1.1 0.5

BES II (MEvts) --- --- --- 400 100 120 80

eCooling factor --- --- --- 8 6 4.5 3

Beam (weeks) --- --- --- 2.0 1.5 3.5 7.5

Add a week between each energy, and BES II program will take about 17 weeks


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A. Fedotov, W. Fischer, private discussions, 2012.

BES Phase-II proposal Electron cooling will provide increased luminosity ~ 10 times Proposal BES-II (Years 2015-2017):

√sNN [GeV] μB [MeV] Requested (Collected) Events(106)

Au+Au 19.6 206 400 (36)

Au+Au 15 256 100 (0)

Au+Au 11.5 316 120 (11.7)

Au+Au 7.7 420 80 (4.3)

U+U: ~20 ~200 100

At current rates, this would take ~70 weeks of RHIC operations!Isn’t there a better way? Yes! We can cool the beams!

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1% Au target

A. Fedotov, W. Fischer, private discussions, 2012.

BES Phase-II proposal Electron cooling will provide increased luminosity ~ 10 times Proposal BES-II (Years 2015-2017):

√sNN [GeV] μB [MeV] Requested (Collected) Events(106)

Au+Au 19.6 206 400 (36)

Au+Au 15 256 100 (0)

Au+Au 11.5 316 120 (11.7)

Au+Au 7.7 420 80 (4.3)

U+U: ~20 ~200 100

- Annular 1% gold target inside the STAR beam pipe - 2m away from the center of STAR- Data taking concurrently with collider mode at beginning of each fill

No disturbance to normal RHIC running

Fixed Target Proposal:

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Fixed Target Set-up

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BES Program Summary

206 5851120 420

2.557.719.639

775

√sNN (GeV)

mB (MeV)

QGP

pro

perti

es

BES

phas

e-I

Test

Run

Fixe

d Ta

rget

BES

phas

e-II

Large range of mB in the phase diagram !!!

Explore QCD Diagram

Timeline for RHIC’s Next DecadeYears Beam Species and Energies Science Goals New Systems Commissioned

2013 • 500 GeV • 15 GeV Au+Au

• Sea antiquark and gluon polarization • QCD critical point search

• Electron lenses • upgraded pol’d source • STAR HFT

2014 • 200 GeV Au+Au and baseline data via 200 GeV p+p (needed for new det. subsystems)

• Heavy flavor flow, energy loss, thermalization, etc.

• quarkonium studies

• 56 MHz SRF • full HFT• STAR Muon Telescope

Detector • PHENIX Muon Piston

Calorimeter Extension (MPC-EX)

2015-2017

• High stat. Au+Au at 200 and ~40 GeV

• U+U/Cu+Au at 1-2 energies

• 200 GeV p+A • 500 GeV

• Extract h/s(Tmin) + constrain initial quantum fluctuations

• further heavy flavor studies • sphaleron tests @ mB0• gluon densities & saturation • finish p+p W prod’n

• Coherent Electron Cooling (CeC) test

• Low-energy electron cooling

• STAR inner TPC pad row upgrade

2018-2021

• 5-20 GeV Au+Au (E scan phase 2)

• long 200 GeV + 1-2 lower s Au+Au w/ upgraded dets.

• baseline data @ 200 GeV and lower s

• 500 GeV • 200 GeV

• x10 sens. increase to QCD critical point and deconfinement onset

• jet, di-jet, g-jet quenching probes of E-loss mechanism

• color screening for different qq states

• transverse spin asyms. Drell-Yan & gluon saturation

• sPHENIX • forward physics upgrades

Steve VigdorDNP Town Meeting

Oct. 25, 2012

Is there another way?

Can another facility do this faster? Or better?

The Alternatives

•Time Line: 2009-2015•Energy Range: √sNN=4.9 - 17.3 GeV •mB = 0.560 - 0.230 GeV

BES I

Runn

+ Running now, that’s good+ Energy range is good- But fixed-target- And light ions Not Ideal

Super Proton Synchrotron (SPS)


Nuclotron based Ion Collider fAcility (NICA)•Time Line: Not yet funded. Plan is to submit documents by end of 2012.

Operations could not begin before 2017 (probably much later)•Energy Range: √sNN = 3.9 - 11 GeV for Au+Au; mB = 0.630 - 0.325 GeV.

Multi-Purpose Detector (MPD)

+ Collider, that’good+ High Luminosity expected• MPD simiar to STAR• Maybe as early as 2017- (But probably later)- Energy is too low!- Will miss the critical point


Facility for Antiproton and Ion Research (FAIR)Time Line:SIS-100 is funded and will be complete by 2018SIS-300 will need additional funding (no time estimate)

Energy Range:SIS-100: Au+Au @ √sNN =2.9 GeVSIS-300: Au+Au √sNN = 2.7 - 8.2 GeV mB =0.730 - 0.410 GeV

Compressed Baryonic Matter (CBM)

STSMVD

TOF

TRDRICH

ECAL

++ Very High Interaction Rate- Fixed target geometry- No time estimate for SIS-300

Probably after 2022- Even with SIS-300, the energy is too low!- Will miss the critical point


SPS

NA61

2009

4.9-17.3

100 HZ

CP&OD

Facilty

Exp.:

Start:

Au+Au Energy:

Event Rate:

Physics:

RHIC BESII

STAR

2017

7.7– 19.6+

100 HZ

CP&OD

NICA

MPD

>2017?

2.7 - 11

<10 kHz

OD&DHM

SIS-300

CBM

>2022?

2.7-8.2

<10 MHZ

OD&DHM

√sNN (GeV)

At 8 GeV

PHENIX

CP = Critical PointOD = Onset of DeconfinementDHM = Dense Hadronic Matter

Comparison of Facilities

Fixed TargetLighter ion collisions

Fixed Target

Conclusion:RHIC is the best optionDaniel Cebra @ APS DNP Meeting – Town Meeting

Newport Beach, CA, 10/26/2012

H.J.Specht, Erice 2012 52

Beam conditions: CERN vs. GSI/FAIR

Luminosity at the SPS comparable to that of SIS100/300 No losses of beam quality at lower energies except for emittance growth RP limits at CERN in EHN1, not in (former) NA60 cave

< 11 – 35 (45) SPS SIS100/300

beam target interaction intensity thickness rate

2.5×106 5×105

[λi ] [Hz] [Hz]

20% NA60 (2003)

new injection scheme

108 10% 107 108 1% 106

interaction rate [Hz]

105 - 107

Energy range: 10 – 158 [AGeV]

LHC AA 5×104

Pb beams scheduled for the SPS in 2016-2017, 2019-2021

How to optimize the physics outcome for the next 10-15 y Proposal: split HADES and CBM at SIS-100

HADES at SIS-100

CBM at SPS

Upgrade HADES, optimized for e+e-, to also cope with Au-Au (now Ni-Ni)

Modify CBM to be optimal (magnet) for either e+e- or μ+μ-; role of hadrons?

Merge with part of personell of CBM

Merge with ‘CERN’ effort towards a NA60 successor experiment

Profit from suitable R&D of CBM

Profit from suitable R&D of CBM, in particular for Si

If SIS-300 would be approved in >2020, one could continue CBM there in >2027H.J.Specht, Erice 2012

G. Usai, CERN Town Meeting 2012

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SummaryResults from BES program covering large mB range

provide important constraint on QCD phase diagram.

Different features show up:– Proton v1 slope changes sign between 7.7 GeV and 11.5 GeV– Particles-antiparticles v2 difference increases with decreasing √sNN

– f-meson v2 deviates from others for √sNN ≤ 11.5 GeV

Search for the critical point continues:- Proposed BES-II program - Fixed target proposal to extend mB coverage up to 800 MeV

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Back up

57

Chemical Freeze-out : Inelastic collision ceases Particle ratios get fixed

★THERMUS : Statistical thermal model Ensemble used – Grand Canonical and Strangeness Canonical

To consider incomplete strangeness equilibration:

Extracted thermodynamic quantities: Tch, mB, ms and gS •Thermus, S. Wheaton & Cleymans, Comput. Phys. Commun. 180: 84-106, 2009.

For Grand Canonical: Quantum numbers (B, S, Q) conserved on average

For Strangeness Canonical: Strangeness quantum number (S) conserved exactly

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Kinetic Freeze-out : Elastic collision ceases Transverse momentum spectra get fixed Blast Wave : Hydrodynamic inspired model

Extracted thermodynamic quantities: Tkin and <β>

E. Schnedermann et al., Phys. Rev. C 48, 2462 (1993)

Particle spectra are fitted simultaneously

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Lattice Gauge Theory (LGT) prediction on the transition temperature TC is robust.

LGT calculation, universality, and models hinted the existence of the critical point on the QCD phase diagram* at finite baryon chemical potential.

Experimental evidence for either the critical point or 1st order transition is important for our knowledge of the QCD phase diagram*.

* Thermalization has been assumed M. Stephanov, K. Rajagopal, and E. Shuryak,

PRL 81, 4816(98); K. Rajagopal, PR D61, 105017 (00) http

://www.er.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf

The RHIC Beam Energy Scan Motivation

http://www.er.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf



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STAR Preliminary

K/p

Particle Ratio Fluctuations

Monotonic behavior of particle ratio fluctuations vs. √sNN

STAR Preliminary

STAR Preliminary

p/p

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Higher Moments: Net-protons

0-5% central collisions: Deviations below Poisson observed for √sNN > 7.7 GeV Peripheral collisions: Deviations above Poisson observed for √sNN < 19.6 GeV Higher statistics needed at 7.7 GeV and 11.5 GeV and possibly a new data point around ~15 GeV

s /

S s ~ /

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Higher Moments: Net-charge

s /

S s ~ /

Data lies in between Poisson and HRG model expectations

Higher statistics needed at 7.7 GeV and 11.5 GeV and possibly a new data point around ~15 GeV

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(C) Searching QCD Critical Point

√sNN

observab

le Enhanced Fluctuationsnear Critical Point

T. Andrews. Phil. Trans. Royal Soc., 159:575, 1869

CO2 nearliquid-gas transition

Particle ratio fluctuations (2nd moments) - K/p, p/p, K/p Conserved number fluctuations - Higher moments of net-protons, net-charge,..

Peak magnetic field ~ 1015 Tesla ! (Kharzeev et al. NPA 803 (2008) 227)

CSE + CME → Chiral Magnetic Wave: • collective excitation• signature of Chiral Symmetry Restoration

RPaddN

ff

sin21

A direct measurement of the P-odd quantity “a” should yield zero.

S. Voloshin, PRC 70 (2004) 057901

Directed flow: expected to be the same for SS and OS

Non-flow/non-parity effects:largely cancel out P-even quantity:

still sensitive to charge separation

Chiral Magnetic effect + Local Parity Violation

66

TPC:Detects Particles in the |h|<1 rangep, K, p through dE/dx and TOFK0

s, L, X, W, f through invariant mass

Coverage: 0 < f < 2p |h| < 1.0Uniform acceptance: All energies and particles

M. Šumbera NPI ASCR 67

Detector performance generally improves at lower energies.

Geometric acceptance remains the same, track density gets lower.Triggering required effort, but was a solvable problem.

Year √sNN [GeV] events(106)

2010 39 130

2011 27 70

2011 19.6 36

2010 11.5 12

2010 7.7 5

2012* 5 Test Run

BES-I Data:

Central Au+Au at 7.7 GeV in STAR TPC

Uncorrected Nch

dNev

t / (N

evt d

Nch

)BES Data Taking

68

STAR TPC - Uniform Acceptance over all RHIC EnergiesAu+Au at 7.7 GeV Au+Au at 39 GeV Au+Au at 200 GeV

Crucial for all analyses

69

Particle IdentificationPID (TPC+TOF):π/K: pT~1.6 GeV/cp: pT~3.0 GeV/cStrange hadrons: decay topology & invariant mass

TPC TPC+TOF

Au+Au 39 GeV

dE/d

x (M

eV/c

m)

70

Charged Hadrons v1: Beam Energy Dependence

Scaling behavior in v1 vs. η/ybeam and v1 vs. η’=η-ybeam

Data at 62.4&200GeV from STAR, PRL 101 252301 (2008)

71

Cou

nts

Cou

nts

Cou

nts

Cou

nts

Cou

nts

Cou

nts

2.94 2.96 2.98 2.94 2.96 2.98

Minv(He3+p )(GeV)2.94 2.96 2.98

Minv(He3+p )(GeV) Minv(He3+p )(GeV)3 3.02 3.04 3.06 3.08 3.1-

02.94 2.96 2.98

60

40

20

100

80

140

120

160Signal

2 / ndf 64.2 / 34Yield 46.43 16.34Mean 2.991 0.001

Run11 27 GeV minbias

3 3.02 3.04 3.06 3.08 3.1Minv(He3+p-)(GeV)

0

60

40

20

120

100

80

160

140

Signal2 / ndf 25.8 / 32Yield 45.57 17.35Mean 2.991 0.001

Run10 7.7 GeV minbias

3 3.02 3.04 3.06 3.08 3.1-

0

10080

60

40

20

160

140

120

220

200

180

240Signal

2 / ndf 41.1 / 32Yield 88.12 20.98Mean 2.992 0.002


3 3.02 3.04 3.06 3.08 3.1Minv(He3+p-)(GeV)

0

60

40

20

120

100

80

160

140

Signal2 / ndf 28.5 / 32Yield 41.18 17.29Mean 2.991 0.001

Run10 11.5 GeV minbias

3 3.02 3.04 3.06 3.08 3.1-02.94 2.96 2.98

100

50

150

200

250Signal

2 / ndf 75.3 / 34Yield 82.91 20.32Mean 2.991 0.000


3 3.02 3.04 3.06 3.08 3.1Minv(He3+p-)(GeV)

02.94 2.96 2.98

40

20

80

60

100

120Signal

2 / ndf 60.7 / 34Yield 42.11 14.00Mean 2.991 0.001


STAR PreliminarySignal

rotated backgroundsignal+background fit

STAR Preliminarysignal










Hypertriton Production

H + H produced at √sNN = 7.7, 11.5, 19.6, 27, 39, 200 GeV (minbias)3L

3L

_

72

Phase Boundary Search With Nuclei

Needs higher statistics to make conclusive statement

Strangeness Population Factor:

Beam energy dependence of S3 behaves differently in QGPand pure hadron gas

- S. Zhang et al., PLB 684 (2010) 224

- J. Steinheimer et al.,PLB 714 (2012) 85

S3 indicates (with 1.7σ )

an increasing trend

73

With 1st

order P.T.Without 1st

Order P.T.

Time evolution of the collision geometry

Kolb and Heinz, 2003, nucl-th/0305084

Initial out-of-plane eccentricity Stronger in-plane pressure gradients drive preferential in-plane expansion Longer lifetimes or stronger pressure gradients cause more expansion and more spherical freeze-out shape

We want to measure the eccentricity at freeze out, εF, as a function of energy using azimuthal femtoscopic radii Rx and Ry:

Evolution of the initial shape depends on the pressure anisotropy ● - Freeze-out eccentricity sensitive to the 1st order phase transition.

Non-monotonic behavior could indicate a soft point in the equation of state.

Spatial eccentricity

74

Azimuthal HBT: First result

Is there a non-monotonic behavior?

sNN (GeV)

J. Phys. G: Nucl. Part. Phys. 38 (2011) 124148

x

75Is the discrepancy due to centrality or rapidity range? - NO

-1.0<y<-0.5-0.5<y<0.50.5<y<1.0

Azimuthal HBT: More Data

…and at LHC

For pT < 8 GeV/c: RAA for p and K are compatible and they are smaller than RAA for proton.For pT > 10 GeV/c: the RAA for p, K and proton are compatible within systematic error.

76

77

RAA of neutral pions

78

RAA(pT) of neutral pions

79

RAA(pT) of neutral pions

beam energy scan program at rhic

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