Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 1

Heavy Flavor as a Probe of Quark-Gluon PlasmaHeavy Flavor as a Probe of Quark-Gluon PlasmaPengfei ZHUANG

Tsinghua University, Beijing

● ● Charm Quark ThermalizationCharm Quark Thermalization ●● J/J/ΨΨ Regeneration in QGP Regeneration in QGP ● ● Effect of Partonic Wind onEffect of Partonic Wind on Dihadron Correlation Dihadron Correlation

with Li Yan, Xianglei Zhu of Tsinghua University, Nu Xu of LBNL,

and Marcus Bleicher, Horst Stoecker of Frankfurt University

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 2

MotivationMotivation

Heavy quarks:Heavy quarks: Produced in initial impact and no extra production during the evolution,Produced in initial impact and no extra production during the evolution, Produced via pQCD process, Produced via pQCD process, Sensitive probe of QGP and rather solid groundSensitive probe of QGP and rather solid ground

Heavy mesons: Heavy mesons: 10-20 c cbar pairs produced at RHIC energy 10-20 c cbar pairs produced at RHIC energy even more than 100 pairs at LHC energy even more than 100 pairs at LHC energy J/J/ΨΨ: : (Thews et. al.)(Thews et. al.) initial production, initial production, suppression, suppression, and regeneration and regeneration

Questions:Questions: 1) are charm quarks thermalized in QGP? 1) are charm quarks thermalized in QGP? 2) Is J/ 2) Is J/ suppressed or enhanced suppressed or enhanced?? 3) are still back-to-back produced at RHIC and LHC? 3) are still back-to-back produced at RHIC and LHC?

DD

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 3

: regeneration in QGP: suppression in QGP

● transverse transport equations in central rapidity region:

● analytic solution

regeneration

relaxation time approximation, neglecting inelastic scatterings

pQCD distribution (Thews,…)

Theoretic FrameTheoretic Frame

thermal distribution

● J/Ψ loss and gain terms via gluon dissociation

via detailed balanceperturbative calculation by Peskin, Bhanot …

initial production and nuclear absorption

anomalous suppression

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 4

● 1+2 dimensional ideal hydrodynamics for light quarks and gluons

● EoS (Sollfrank,…) ideal QGP phase and ideal hadron phase

● Initial condition of hydrodynamics: determined by nuclear geometry (Kolb, Heinz, Rapp,…)

● Parameters at RHIC

Theoretic FrameTheoretic Frame

● D meson production Langevin equation for charm quark motion:

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 5

Charm Quark ThermalizationCharm Quark Thermalization

thermal

pQCD

charm quark Pt distribution

low Pt charm quarks are easily thermalized, but high Pt charm quarks are hard to get thermalized.

charm quark V2

decreasing D meson V2 at high Pt means non-thermalized high Pt charm quarks

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 6

initial production still dominates the yield in semi-central collisions, but regeneration is definitely important in central collisions ! see also Rapp, Grandchamp, Brown, 2004, 2005

J/J/ΨΨ Regeneration in QGP Regeneration in QGP

small V2 due to dominance of initial production

initially produced J/ψ are all eaten up by QGP,regeneration dominates J/ψbehavior at any centrality

Yan, Zhuang, Xu: PRL97,232301(2006)

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 7

DDEffect of Partonic Wind on Correlation Effect of Partonic Wind on Correlation

● back-to-back production in hadron-hadron interactionback-to-back production in hadron-hadron interactionDD

● what is the correlation at RHIC and LHC?what is the correlation at RHIC and LHC?

● hadronic re-scattering has little effects on hadronic re-scattering has little effects on correlation (UrQMD)correlation (UrQMD)

● how does the QGP modify the angular how does the QGP modify the angular correlation?correlation?

DD

DD

DD

● when charm quarks are thermalized, the collective when charm quarks are thermalized, the collective expansion will push and to move in the same expansion will push and to move in the same direction !direction !

● at RHIC, the back-to-back correlation is washed out at RHIC, the back-to-back correlation is washed out by the partonic collectivity.by the partonic collectivity. ● at LHC, the NLO contribution, the fast thermalization of at LHC, the NLO contribution, the fast thermalization of charm quarks, and the strong partonic wind change the charm quarks, and the strong partonic wind change the production from back-to-back correlation to near production from back-to-back correlation to near side correlation !side correlation !

D

DD

D

Zhu, Bleicher, Huang, Schweda, Stoecker, Xu, Zhuang, PLB647, 366(2007)

Pengfei ZHUANG INPC’07, Tokyo, June 3-8, 2007 8

● only low Pt charm quarks can be thermalized.only low Pt charm quarks can be thermalized.

● J/J/ΨΨ: a smoking gun at LHC: a smoking gun at LHC RHIC: both initial production and regeneration, still J/Ψ suppression and small V2 LHC: almost only regeneration, J/Ψ enhancement and large V2

● ● correlation: a sensitive signal of QGPcorrelation: a sensitive signal of QGP RHIC: almost no correlation

LHC: from back-to-back to near side correlation

SummarySummary

DD