J/ψ: a Hard and a Soft Probe of QGP
Pengfei ZHUANG, [email protected]
thanks to Dr. Nu XU and my students Baoyi CHEN, Gang LI, Yunpeng
LIU , Zhen QU, Li YAN, Kai ZHOU and Xianglei ZHU
The 9th Workshop
on QCD Phase Transitions and Relativistic Heavy Ion Collisions
&
The Workshop on Jet Physics
17-21 July 2011, Hangzhou, China
Quarkonium in Vacuum
Heavy Quark as a Probe of QGP
electron as a probe of nucleon
structure at CEBAF
heavy quark as a probe of QGP
structure at FAIR, SPS, RHIC and LHC
●quarkonia can survive inside the QGP,
a sensitive signature of QGP formation
●heavy quarks are produced via hard processes,
rather solid theoretical ground
Matsui and Satz: PLB178, 416(1986):
J/Psi suppression as a probe of QGP in HIC
A Hard and a Soft Probe of QGP
charmonium regeneration:
PBM,Stachel, PLB2000,
Thews,Mangano, PRC2001,
Zhao, Rapp, 2008
Hot nuclear matter effects:
1)suppression in QGP and HG
2)regeneration in QGP and HG
hot medium formation
Cold nuclear matter effects:
1)nuclear absorption
2)Cronin effect
3)shadowing effect
●regeneration is important for central collisions and low pt particles,
●initial production dominates peripheral collisions and high pt particles.
What is Sensitive to the Production and
Suppression Mechanism ?
for J/psi yield, almost all the models – with and
without the assumption of QGP and with and
without regeneration mechanism – can describe
the observed suppression, after at least one
parameter is adjusted.
the transverse momentum distribution, which
depends more directly on the production
mechanism, may contain additional information
about the nature of the medium and J/psi and
may help to distinguish between different
scenarios.
A Detailed Transport Approach for Quarkonia in HIC
Yan, Zhu, Xu, Zhuang, PLB2005, PRL2006
●the quarkonium distribution function in phase space
f ( p, x , t )
●the quarkonium transport equation ( can be solved analytically )
gluon dissociation cross section
by OPE (Peskin,1999)
●initial distribution
regeneration by detailed balance
f ( p, x, t0 ) including CNM
●hydrodynamics for medium evolution
+ equation of state (ideal gas or
strongly coupled matter from lattice)
Dissociation Temperature TD in Potential Model
Lattice calculated free energy F for a pair of QQ
two limits of the potential:
slow dissociation
F ,
V (r , T )  
U  F  TS , rapid dissociation
Schroedinger equation at finite T:
average distance
binding energy
r (T )
 (T )
dissociation temperature:
r (TD )  ,  (TD )  0
for V=U (Satz et al)
Dissociation Cross Section
J / ()  g  Q  Q
gluon dissociation cross section described by OPE (Peskin,1999)
 ( p , pg )
at finite temperature
 ( p , pg , T )
dissociation rate of
/E
r 2 (T )
2
r (0)
 ( p , pg )
 at a fixed medium velocity v=0.5 and for V=U
Initial Condition
●initial condition for hydrodynamics:
by fitting the light hadron multiplicity
RHIC :   0.6 fm,
T0  340 MeV
LHC :   0.4 fm,
T0  515 MeV
●initial condition for transport equation: f ( p, x , t0 )
supposition of pp collisions, including CNM.
suppose  coll   QQ   QGP , nuclear absorption can be neglected, we
consider only Cronin effect (and shadowing effect).
Cronin effect:
gluons multi-scattering with nucleons before they fuse into a bb pair.
transverse momentum
broadening !
J/ψ RAA ( pt ) at RHIC
Liu, Qu, Xu, Zhuang: arXiv:0901.2757,PLB2009
regeneration contribution is important only for low pt,
high pt is controlled by initial production.
two J/ψ puzzles at RHIC
Liu, Xu, Zhuang: arXiv:0907.2723,JPG2010
more regeneration in central rapidity than in forward rapidity
J/ψ RAA ( Np ) at high pt at RHIC
STAR data, QM2011
high pt particles can survive in dense medium.
J/ψ RAA ( pt ) for central and semi-central collisions at RHIC
STAR data, QM2011
more suppression in central collisions
J/psi elliptic flow at RHIC
impact parameter b=7.8 fm
STAR data, QM2011
Yan, Xu, Zhuang: nucl-th/0608010,PRL2006
no J/psi V2 at RHIC !
J/ψ RAA ( Np ) at LHC
From Cold to Hot Nuclear Matter Effect
Cold Nuclear Matter Effect
Hot Nuclear Matter Effect
Zhou, Xu, Zhuang, NPA2011
Υ, a Cleaner Probe at RHIC
J/ψ :
the production and suppression mechanisms are complicated:
there are primordial production and nuclear absorption in the
initial state and regeneration and anomalous suppression
during the evolution of the hot medium.
Υ:
1)the regeneration at RHIC can be safely neglected;
Grandchamp, Lumpkins, Sun, van Hees and Rapp, PRC2006
2)there is almost no feed-down forΥ ;
3) RAA 1 in d+Au means negligible nuclear absorption.
Liu for STAR Collaboration, NPA2009
Υat RHIC: RAA( Np )
Liu, Chen, Xu, Zhuang: arXiv:1009.2585,PLB2011
for minimum bias events:
PHENIX dada: RAA<0.64 (NPA2009)
our result: RAA = 0.63 for V=U
RAA= 0.53 for V=F
●ground state is not affected by the medium
Au+Au at √s=200 GeV
●excited states are sensitive to the medium, and the data support V=U
Υat RHIC: RAA( pt )
Liu, Chen, Xu, Zhuang: arXiv:1009.2585,PLB2011
central Au+Au at √s=200 GeV
● strong Cronin effect for survived ground state
● no pt dependence for disappeared excited states
Υat RHIC:
pt2 ( N p )
relation between ϒ at RHIC and J/ψ at SPS:
● no ϒ regeneration at RHIC and no J/ψ regeneration at SPS
●
TD (1s )  4Tc  TRHIC
no ϒ(1s) suppression at RHIC
TDJ /  2Tc  TSPS
no J/ψ suppression at SPS
both are controlled by the Cronin effect !
 pt2  pt2
2 RHIC
t 
 p

AA
 pt2
RHIC
agN
RAu
a
SPS
gN
RPb
pp
 agN L
2 SPS
t J /
 p
2 SPS
t J /
 2.4 p
Au+Au at √s=200 GeV
Liu, Chen, Xu, Zhuang: arXiv:1009.2585,PLB2011
Υat LHC: RAA( Np )
our calculation without regeneration
for minimum bias events:
regeneration becomes important at LHC !
Measuring RHIC Temperature by Excited ϒ States
initial temperature dependence of RAA
central Au+Au at √s=200 GeV
Liu, Chen, Xu, Zhuang: arXiv:1009.2585,PLB2011
suppression of excited ϒ states is sensitive to the fireball temperature !
Conclusions:
● pt dependence is more sensitive to the production
and suppression mechanism.
● regeneration is important at RHIC and becomes
dominant at LHC.
● excited Υstates are cleaner probes of QGP.
● RHIC data supports heavy quark potential V=U
Uncertainty analysis:
pp collision, shadowing effect, EoS, time scales, ……
Suggestions:
● measuring D-Dbar correlation at LHC (Zhu, Bleicher, Huang,
Schweda, Stoecker, Xu, Zhuang, PLB2007, Zhu, Xu, Zhuang, PRL2008)
● measuring J/psi-D correlation at LHC (since both are from the
same source, talk by Gang Li, 18th )
● measuring quarkonium v2 at LHC (which is very sensitive to the
production and suppression mechanisms, talk by Yunpeng Liu, 20th ).
23
BACKUP
Only Cold Nuclear Matter Effect ?
No !
RHIC Pt distribution needs hot medium effect!
At LHC, cold effect disappears in the final state !
Dependence on EoS
J/Psi Pt distribution at LHC where EoS plays an essential role!
wQGP
sQGP
D D Correlation
NN collisions: back-to-back correlation
RHIC: almost no correlation
LHC: near-side correlation
27
RHIC low pt is similar to LHC high pt ?
J/ψ RAA ( pt ) at LHC
Υat LHC: RAA( pt )
high pt is controlled by initial production !