用重味探测夸克胶子等离子体 Heavy Flavor as a Probe of Quark-Gluon Plasma Pengfei ZHUANG (庄鹏飞) Tsinghua University, Beijing (清华大学，北京) 1.引言 Motivation 2.论证 Heavy Flavor Transport in QGP 3.结果 J/Ψ Production and Correlation 4.总结 Summary with Li YAN (严力), Xianglei ZHU(朱相雷) of Tsinghua and Nu XU (许怒) of LBNL PRL97, 232301(2006) PLB, in press Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 1. Motivation Heavy quarks: Produced in initial impact and no extra production at hadronization Probe of high dense phase (QGP) Production via pQCD process Rather solid ground Heavy mesons: 10-20 c cbar pairs produced at RHIC energy J/Ψ and : initial production, suppression and regeneration Questions: 1) What is the dominant production mechanism? 2) Is J/  suppressed or enhanced? 3) What is the difference between RHIC and LHC? Lattice, QM06 J/Ψcan survive till 1.6 Tc ! Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 2. Transport of Heavy Flavor in QGP our treatment J/Ψ: ● both initial production and continuous regeneration in QGP ● suppression and regeneration via gluon dissociation and the inverse process ● transport equations for J/Ψ and charm quark + hydrodynamic equation for QGP D: ● formation on the hadronization hypersurface via coalescence Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 2. Transport of Heavy Flavor in QGP ● transverse transport equations in central rapidity region: : suppression in QGP relaxation time approximation : continuous regeneration in QGP ● analytic solutions first term: initial production, second term: continuous regeneration, both suffer suppression in QGP ● initial conditions: pQCD distribution (Thews,…) energy and momentum conservation determine T and uu Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 2. Transport of Heavy Flavor in QGP ● J/Ψ loss and gain terms via gluon dissociation perturbative calculation with nonrelativistic Coulomb potential (Peskin, Bhanot …) via detailed balance ● 1+2 dimensional ideal hydrodynamics of QGP in gluon distribution ● EoS (Sollfrank,…) ideal QGP phase and ideal hadron phase ● Initial condition of hydrodynamics: determined by nuclear geometry (Kolb, Heinz, Rapp,…) ● Parameters at RHIC Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation ● J/Ψ yield PHENIX data nucl-ex/0611020 hep-ex/0611020 initial production and regeneration are equally important in central collisions, initial production dominates the yield in semi-central collisions, not sensitive to the charm quark distribution. see also Rapp, Grandchamp, Brown, 2004, 2005 Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation ● J/Ψ transverse momentum PHENIX data nucl-ex/0611020 hep-ex/0611020 regeneration is definitely important in central collisions Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation ● J/Ψ V2 at b=7.8 fm 1) initial V2 is small 2) regenerated V2 is large 3) total V2 is small due to dominance of initial production *V2 can differentiate initial production from regeneration, *V2 can answer the question if charm quarks are thermalized, *V2 can differentiate sudden from continuous regeneration Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation ● ratio of regenerated to initially produced J/Ψ’s at LHC initially produced charmoniums are all eaten up by QGP, the regeneration dominates the charmonium behavior at any centrality 1) enhanced at LHC 2) large at LHC Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation ● Similar to jets, C and Cbar (D and Dbar) should have strong back-to-back angular correlations. ● The NLO contribution becomes dominant at LHC! There are no more obvious back-to-back correlations ● Hadronic re-scattering has little effects on DDbar correlations (UrQMD) ● How does the QGP modify the angular correlation? Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 3. J/Ψ and Correlation RHIC most central LHC most central ● at RHIC, the back-to-back angular correlations are washed out by partonic collectivity. ● At LHC, larger partonic density, higher temperature, stronger collective expansion The partonic wind pushes produced C and Cbar to near side! From back-to-back correlation to near side correlation ! Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

China-France Workshop on LHC, Beijing, Dec.11 –15, 2006 4. Summary ● J/Ψ: a smoking gun at LHC RHIC: both initial production and regeneration are important J/Ψ suppression and small V2 LHC: regeneration dominates everything J/Ψ enhancement and large V2 ● D Dbar correlation: a signal sensitive to QGP RHIC: back-to-back correlation disappears LHC: from back-to-back to near side correlation Thanks for your patience Pengfei ZHUANG China-France Workshop on LHC, Beijing, Dec.11 –15, 2006