rnm meeting fias, frankfurt, 22 feb 2006 1 hunt for the qgp at rhic kai schweda, university of...

1 RNM meeting FIAS, Frankfurt, 22 Feb 2006

Hunt for the QGP at RHIC

Kai Schweda, University of Heidelberg

S. Blyth, A. Dainese, T. Dietel, X. Dong, J. Faivre, Y. Lu, M. Oldenburg, H.G. Ritter, L. Ruan, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.


Outline

1) Introduction

2) High-pT Suppression

3) Bulk properties:

- Hadron abundances

- Heavy-Flavor (c,b) Collectivity

4) Summary


Quark Gluon Plasma

Source: Michael Turner, National Geographic (1996)

Quark Gluon Plasma:

(a) Deconfined and

(b) thermalized state of quarks and gluons

Study partonic EOS in high energy nuclear collisions(?) Probe thermalization using heavy-quarks


Phase Diagram

RNM meeting FIAS, Frankfurt, 22 Feb 2006

Au +Au @ 20, 62, 130, 200 GeV

Cu + Cu @ 20, 62, 200 GeV

d + Au @ 200 GeV

p + p @ 200, 400 GeV


Peripheral Event

STARSTAR

Au + Au Collisions at RHICAu + Au Collisions at RHIC

(real-time Level 3)

7 RNM meeting FIAS, Frankfurt, 22 Feb 2006STARSTAR

Mid-Central Event


(real-time Level 3)



STARSTAR

Central Event

(real-time Level 3)


Collision Geometry, Flow

x

z

Non-central Collisions

Number of participants: number of incoming nucleons in the overlap regionNumber of binary collisions: number of inelastic nucleon-nucleon collisions

Charged particle multiplicity collision centralityReaction plane: x-z plane

Au + Au sNN = 200 GeV (|| < 0.75)


Hadron spectra from RHICp+p and Au+Au collisions at 200 GeV

White papers - STAR: Nucl. Phys. A757, p102;


Two Different Ways to Probe Bulk

Use high pT as probe Probe the bulk response

Partons lose energy in medium

Response of medium to pressure

Measure nuclear modification factor RAA

Measure elliptic flow v2

Partonic energy lossdE/dx, gluon density

Partonic equation of stateEoS

I believe, they are all correlated: back-back, R_AA, v2,… Interactions !


Fast partons emits gluons energy loss

Energy loss depends on color charge density

Measure E color (~gluon) density in dense phase

Dominant Process:Gluon Bremsstrahlung

hadronsleadingparticle suppressed

q

q

?

Partonic Energy Loss


hadrons

leadingparticle suppressedq

q

?

After the initial hard-scattering, the parton interacts

strongly with the dense medium in central Au+Au collisions

Observation of Jet Quenching


Energy Loss and Equilibrium

Leading hadrons

Medium

Suppression at intermediate pT - caused by final state interactions

Energy loss leads to progressive equilibrium in Au+Au collisions


Photon – Hadron Correlations*

*STAR analysis: T. Dietel; nucl-ex/0510046.

First high-pT correlations !

No background subtraction !

Same-side: increasing

contributions from -jet events

Away-side: different

suppression for di-jet vs -jets

First step towards -

jet

Detailed energy loss

studies !


If no “effects”: R < 1 in regime of soft physics R = 1 at high-pT where hard scattering dominates Suppression ? Is R < 1 at high-pT ?

Nuclear Modification Factor

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

Quantify deviations from expected behaviour in p+p collisions:

<Nbinary>/inelp+p (Nuclear

Geometry)


Large Suppression in central Au + Au

Suppression is absent in d-Au collisions

Final state effect Partonic energy loss

Initial or Final State?


Heavy-flavor Energy Loss

Heavy-flavor decay electrons:

Probe interaction with medium

b,c e + X

Induced gluon radiation only

Plus elastic collisions

Better agreement with data

Heavy flavor energy loss not fully understood !

Calculations: M. Djordjevic et al.


Partonic Energy Loss at RHIC

(1) Intermediate/high pT: spectra suppressed and ratios start to decrease at pT

~ 2 GeV/c

(2) Jet-like behavior observed in correlations

- hard scatterings in AA collisions

- disappearance of back-to-back correlations

- energy gets largely deposited in the bulk medium

Partonic energy loss at RHIC !

(3) Heavy-flavor energy loss:

- Experimental program just started Next step: Fix partonic EOS !

RNM meeting FIAS, Frankfurt, 22 Feb 2006

Hadro Chemistry

Tch = 163 4 MeV, b = 24 4 MeV

In central collisions: no need for S !

Resonances do not fit: Hadronic life !

White papers:STAR: Nucl. Phys. A757, p102;PHENIX: p184 (2005).


Elementary p+p Collisions

Low multiplicities

use canonical ensemble:

Strangeness locally

conserved!

particle yields are well

reproduced

Strangeness not

equilibrated ! (s = 0.5)

Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).


Pressure, Flow, …Pressure, Flow, …

pdVdUd Thermodynamic identity

– entropy p – pressureU – energy V – volume= kBT, thermal energy per dof

In A+A collisions, interactions among constituentsand density distribution lead to: pressure gradient collective flow

number of degrees of freedom (dof) Equation of State (EOS) cumulative – partonic + hadronic


Momentum Momentum Distributions*Distributions*

2

][(

GeV

/

2c)

-1

dydp

Nd

T

][GeV/ cpT

K (dE/dx)

p

K (kink)

*Au+Au @130 GeV, STAR

Tth=107±8 [MeV]

<t>=0.55±0.08 [c]

n=0.65±0.09

2/dof=106/90

solid lines: fit range

• Two-parameter fit describes yields of

, K, p,

• Tth = 90 10 MeV

• <t> = 0.55 0.08 c

Disentangle

collective motion from thermal random walk

K (dE/dx)

p

K (kink)


Kinetic Freeze-out at RHIC1) ,K and p change smoothly from

peripheral to central collisions.

2) At the most central collisions, <T> reaches 0.6c.

3) Multi-strange particles , are found at higher T and lower <T>

Sensitive to early partonic stage!

What about v2 ?

4) Single sudden freeze-out*: all collectivity from partonic stage!

STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04). *A. Baran, W. Broniowski and W. Florkowski; nucl-th/0305075.


Anisotropy Parameter v2

y

x

py

px

coordinate-space-anisotropy momentum-space-anisotropy

y 2 x 2y 2 x 2

v2 cos2 , tan 1(pypx

)

Initial/final conditions, EoS, degrees of freedom


v2 in the Low-pT Region

P. H

uo

vi ne

n, p

r ivate

com

mu

nica

t i on

s, 20

04

- Minimum bias data! At low pT, model result fits mass hierarchy well!- Details do not work, need more flow in the model!


Collectivity, Deconfinement at RHIC

- v2, spectra of light hadrons and multi-strange hadrons - scaling with the number of constituent quarks

At RHIC, I believe we have:

Partonic Collectivity

Deconfinement

Thermalization ?

PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04),

PRL95, 122301(05).

S. Voloshin, NPA715, 379(03)Models: Greco et al, PRC68, 034904(03)X. Dong, et al., Phys. Lett. B597, 328(04).


v2 of Multi-strange Hadrons

Strange-quark flow partonic collectivity at RHIC!

QM05 conference: M. Oldenburg; nucl-ex/0510026.


meson Flow at RHIC

QM05 conference: M. Oldenburg; nucl-ex/0510026.

Strange-quark flow partonic collectivity at RHIC!


RQMD results, absolute numbers

too low need partonic flow !

However:

1) At low pT region:

hydro-type mass ordering

2) Intermediate pT:

baryon/meson ordering

3) Hadronic vacuum X-sections!

4) The number of constituent

quark scaling may not be unique!

Y. Lu et al., nucl-th/0602009.

Hadronic Transport Model


Partonic Collectivity at RHIC

1) Copiously produced hadrons freeze-out ,K,p: Tfo = 100 MeV, T = 0.6 (c) > T(SPS)

2) Multi-strange hadrons freeze-out: Tfo = 160-170 MeV (~ Tch), T = 0.4 (c)

3) Multi-strange v2: Multi-strange hadrons , and do flow!

4) Constituent Quark scaling: Seems to work for v2 and RAA (RCP)

Deconfinement &Partonic (u,d,s) Collectivity !


Heavy-Flavor Quarks

Plot: B. Mueller, nucl-th/0404015.

Symmetry is broken:

QCD dynamical mass

EW Higgs mass

Even in a QGP, charm and

beauty quark-mass heavy !

If heavy quarks flow:

frequent interactions

among all quarks

light quarks (u,d,s)

likely to be thermalizedPlot: B. Mueller, nucl-th/0404015.

Mas

s (M

eV/c

2 )

106

105

104

103

102

10

1


The key point is to determine

Heavy-Flavor CollectivityD0, D, D+

s, +C, J/, …


Charm(Bottom) e Spectrum

Three independent analyses

using different sub-detectors

σcc = 1.4 0.2 0.4 mb

PHENIX, Au+Au:

cc= 0.62 0.06 0.16 mb

Need direct open charm

reconstruction !

(D0 K + )EMC -- STAR preliminary

STAR: PRL 94, 062301 (2005);PHENIX: PRL 94, 082301 (2005).


Non-photonic electron v2

c (b) e + X

Large syst. uncertainties due to large background

Experimental data do not agree at 2<pT(e)<5 GeV/c!

v2(e) favors non-zero v2(c) at pT(e)<2 GeV/c.

V. Greco et al.PLB 595(2004)202

B. Zhang et al.nucl-th/0502056


J/Enhancement at LHC Statistical hadronization

strong centrality dependence

of J\ yield at LHC (and RHIC?)

slope ~ cc

Need total charm yields !

Measure D0, D±, c, c

Probe deconfinement

and thermalizationCalculations:P. Braun Munzinger, K. Redlich,and J. Stachel, nucl-th/0304013.


J/ at RHIC

P. Braun-Munzinger et al.

Yellow band: allowed

range by open charm

from STAR and PHENIX

Large uncertainty from

open charm cross section !

Need precise open

charm reference !


Chiral Doubling

P. Braun-Munzinger et al.M. Novak, Int. J. Mod. Phys. A20 (2005) 229.

Assume chiral doubling in

charm sector

Still large uncertainties

Need precise open

charm reference !

Direct open charm

reconstruction


D Meson Pair Correlations

Pythia Calcs.: H. Woehri, priv. comm.

Hadronic Transport Model:E.L. Bratkovskaya et al., PRC 71 (2005) 044901.

ccbar pair production: DDbar

pairs are correlated !

Here: correlation

If charm equilibrates

correlations vanish !

Influence of hadronic

scattering (small) ?


Summary Intermediate/high-pT:

partonic energy loss

Elliptic flow of multi-strange hadrons :

partonic collectivity

Colored medium created at RHIC !

Status of Thermalization ?

Measure elliptic flow, spectra and yields of

D0, D, D+s,

C, J/


STAR MRPC - TOF

STAR MicroVertex Tracker Active pixel sensors (APS) Two layers of thin silicon

- Full open charm measurements- Full resonance measurements with both hadron and lepton decays

STAR Upgrades

rnm meeting fias, frankfurt, 22 feb 2006 1 hunt for the qgp at rhic kai schweda, university of...

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