1. 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 论证 Heavy Flavor Transport in QGP 结果 J/Ψ Production and Correlation 总结 Summary
with Li YAN (严力), Xianglei ZHU(朱相雷) of Tsinghua and Nu XU (许怒) of LBNL
PRL97, (2006) PLB, in press
Pengfei ZHUANG
China-France Workshop on LHC, Beijing, Dec.11 –15, 2006

2. 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: c cbar pairs produced at RHIC energy
J/Ψ and : initial production, suppression and regeneration
Questions: ) What is the dominant production mechanism? ) Is J/  suppressed or enhanced? ) 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

3. 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

4. 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

5. 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

6. China-France Workshop on LHC, Beijing, Dec.11 –15, 2006
3. J/Ψ and Correlation
● J/Ψ yield
PHENIX data nucl-ex/ hep-ex/
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

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

8. 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 ) regenerated V2 is large ) 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

9. 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

10. 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

11. 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

12. 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 V 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