1、Round Table Workshop on NICA Physics Dubna,September 9-12,2009,1,J/ Production in Heavy Ion Collisions Pengfei ZHUANG Tsinghua University, BeijingIntroductionJ/ at SPSJ/ at RHICJ/ at NICA,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,2, produced only in the initial impact, and no ex
2、tra production in the later evolution a probe of early thermalization and a probe of QGP produced via hard process rather solid ground,importance of heavy quarks,B.Mueller, nucl-th/0404015,Matsui and Satz 1986: J/ suppression as a signature of QGP formation in HI,Round Table Workshop on NICA Physics
3、 Dubna,September 9-12,2009,3, both initial production and regeneration both normal suppression and anomalous suppression,J/ motion in heavy ion collision,hot nuclear matter effects,cold nuclear matter effects,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,4,J/ at SPS: normal suppress
4、ion,mechanism: multi-scattering between J/ and spectator nucleonsR.Vogt, Phys.Rept.310, 197(1999) C.Gerschel, J.Hufner, Annu.Rev.Nucl.Part.Sci. 49, 225(1999),conclusion: nuclear absorption can well explain the J/ yield in p-A and light nuclear collisions at SPS energy !,NA38,Round Table Workshop on
5、NICA Physics Dubna,September 9-12,2009,5,model 1: Debye screening (Matsui & Satz, 1986),NA38,at T=0,at T 0,J/ at SPS: anomalous suppression,model 2: threshold model (Blaizot, Dinh, Ollitrault, 2000),model 3: comover interaction Capella, Feireiro, Kaidalov, 2000),Round Table Workshop on NICA Physics
6、Dubna,September 9-12,2009,6,J/ at RHIC: regeneration,there are about 10 pairs of c quarks in a central Au-Au collision at RHIC energy and more than 100 pairs at LHC energyimportant J/ regeneration at high energies: in QGP in hadron gasthe competition between J/psi suppression and regeneration leads
7、to the question: J/ suppression or enhancement at high energies?model 1: statistical production at Tc, no initial productionAndronic, PBM, Redlich, Stachel, 2007,mesons,model 2: continuous production inside QGP with anomalous suppression, no initial production Thews, Mangano, 2006,model 3: two-compo
8、nent model, initial production + regeneration Grandchamp, Rapp, Brown, 2004regeneration in hadron gas is important too Bratkovskaya, Cassing, Stoecker, 2003,the competition between suppression and regeneration explains well the data,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,7,J/
9、 at RHIC: is regeneration necessary ? I,J/ puzzle 1: almost the same suppression at SPS and RHIC !,Kaczmarek et al., 2003,explanation without regeneration: Schroedinger equation for c cbar with lattice potential gives the charmonium dissociation temperature: Karsch, Kharzeev, Satz, 2006,if TSPS TRHI
10、CTJ/ , the suppression at SPS and RHIC will be the same and it explains the puzzle 1. it looks not necessary to introduce the regeneration .,explanation with regeneration: at RHIC, stronger suppression and stronger regeneration,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,8,J/ at R
11、HIC: is regeneration necessary ? II,J/ puzzle 2: stronger suppression at forward rapidity !,explanation with regeneration: stronger regeneration at mid rapidity Liu, Xu, Zhuang, 2009,mid-rapidity,forward rapidity,explanation without hot nuclear matter effects: different J/ production in pA and AA fr
12、om pp Kharzeev, Levin, Nardi, Tuchin, 2009 strong J/ suppression even at T=0 !,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,9,transport model (Hufner, Zhuang, 2003; Zhu, Xu, Zhuang, 2005): transport equation for J and hydrodynamics for QGP,for J/ yield, almost all the models with a
13、nd without the assumption of QGP and with and without regeneration mechanism describe the observed suppression, after at least one parameter is adjusted. the transverse momentum distribution which depends more directly on the production and suppression mechanisms contains more information on the nat
14、ure of the medium and J/ and may help to distinguish between different scenarios.,J/ at SPS: transverse momentum,suppression,regeneration,no regeneration at SPS,very important leakage effect !,pt enhancement at SPS,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,10,J/ at RHIC: transve
15、rse momentum,Yan, Xu, Zhuang, 2006; Liu, Xu, Zhuang, 2009,low pt is controlled by both initial production and regenerationhigh pt enhancement is induced by Cronin effect in initial production initial production + regeneration explain both the yield and transverse momentum distribution,pt broadening,
16、pt suppression,strong pt suppression,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,11, LHC: almost only regeneration, sensitive to hot nuclear matterRHIC: both initial production and regeneration the calculation needs a quite accurate fine-tuning between the two production mechanism
17、s SPS: almost only initial productionNICA: only initial production, sensitive to cold nuclear matter,J/ at NICA: cold nuclear matter effects, is the rapidity dependence at NICA similar to that at RHIC? 2 gluon fusion mechanism: no3 gluon fusion mechanism: yes (Kharzeev et al., 2009)the rapidity depe
18、ndence can distinguish from the initial production mechanisms, normal vs anomalous suppression at NICA longer collision time (1 fm), important (dominant) nuclear absorption,shorter life time of hot matter, weaker anomalous suppression,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,12
19、, pt distribution at NICALHC: strong pt suppression due to thermalized regeneration NICA: strong pt enhancement due to Cronin effect ( gluon multi scattering ) and leakage effect ( high momentum particles can escape the hot medium ).the life time of hot matter is short at NICA but long at RHIC and L
20、HC, the leakage effect is therefore more important at NICA.,J/ at NICA: others, mixed phase at NICA the phase transition at NICA may be of first order life time of mixed phase fraction of anomalous suppression RHIC 4.5 fm 7% SPS 5 fm 30%long life time of mixed phase and short life time of quark matt
21、er the suppression in the mixed phase becomes more important at NICA !,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,13,conclusion,cold and hot nuclear mater effects on J/ in high energy nuclear collisions are still not clear at NICA: 1) Transverse momentum and rapidity distribution
22、s can distinguish from J/ production mechanisms: * pt enhancement due to Cronin effect and strong leakage effect * stronger suppression at forward rapidity (3 gluon fusion) or at mid rapidity (2 gluon fusion)? 2) Nuclear absorption dominates the J/ suppression and anomalous suppression happens mainl
23、y in the mixed phase 3) non-thermalized J/ has small (zero) elliptic flow.,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,14,thanks for your attention,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,15,centrality dependence at SPS,Zhu, Zhuang, PRC67, 067901(2003),J/psi
24、 R_AA and at SPS energy as functions of centrality and p_t can be well described by nuclear and medium absorption, without regeneration.,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,16,dominant regeneration at LHC,while initial production and regeneration are equally important at R
25、HIC, the J/psi yield at LHC is characterized by the regeneration only!,* J/psi is controlled by regeneration * J/psi yield at LHC increases with centrality,Liu, Xu, Zhuang, PLB, 2009 and QM2009,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,17,initial production & nuclear absorption
26、are included in initial condition,Round Table Workshop on NICA Physics Dubna,September 9-12,2009,18,near side correlation in sQGP,we take drag coefficient to be a parameter charactering the coupling strength,* c quark motion in QGP:,* QGP evolution: ideal hydrodynamics,for strongly interacting quark
27、-gluon plasma: at RHIC, the back-to-back correlation is washed out. at LHC, c quarks are fast thermalized, the strong flow push the D and Dbar to the near side!,Zhu, Xu, Zhuang, PRL100, 152301(2008),large drag parameter is confirmed by R_AA and v_2 of non-photonic electrons (PHENEX, 2007; Moore and Teaney, 2005; Horowitz, Gyulassy, 2007).,
