Transcript Probing the QGP with Quarkonium

J/Ψ TMD as a Sensitive Signature of QGP
Pengfei Zhuang (Tsinghua University, Beijing)
● The J/ψ Puzzle
● A Full Transport Approach
● Running Dissociation Temperature
● Summary and Outlook
Collaborated with Dr. Nu Xu and Yunpeng Liu, Kai Zhou, and Xianglei Zhu
STAR Regional Meeting, Weihai, July, 2012
J/ψ Puzzle
Result:
the yields at SPS, RHIC and LHC
have similar trend.
Question:
is J/ψ still a sensitive signature
of the QGP ?
62 GeV

Transverse Momentum Distribution
Pt distribution is sensitive to the dynamics of the system
and should tell us more about the nature of the medium !
Data and Our Model Prediction
A Full Transport Approach for Quarkonia in HIC
Yunpeng Liu, Nu Xu, Kai Zhou, Xianglei Zhu, PZ, 2005-2012
to study the J/ψ interaction with QGP, we need a
dynamic description for both J/ψ and QGP !
● QGP hydrodynamics
 T   0,
  n  0
+ equation of state
● quarkonium transport equations
α: suppression β: regeneration
● analytic solution
● initial production f ( p, x , t0 ) , including CNM.
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Dissociation Cross Section
J / ()  g  Q  Q
● gluon dissociation cross section calculated by OPE (Bhanot, Peskin,1999):
 ( p , pg )
● at finite temperature, we use the classical relation
 ( p , pg , T ) 
r 2 (T )
r 2 (0)
 ( p , pg )
r 2 (T ) is calculated through the
Schroedinger equation
● J/Ψ dissociation rate
● regeneration rate is determined by the detailed balance
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Charm Quark Distribution
Due to interaction with the medium, charm quarks become soft in the
medium, and therefore the regeneration happens only in the low pt region.
From observed D-meson flow at RHIC, charm quarks seem to be thermalized,
we take thermal distribution for charm quarks in the medium.
Initial fraction and regeneration fraction for J/Ψ produced in central Pb+Pb
collisions at LHC energy, with thermal charm quark distribution.
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Prediction at RHIC (1)
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Prediction at RHIC (2)
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Prediction at LHC (1)
the talks by Kai Zhou and Baoyi Chen this evening
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Prediction at LHC (2)
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Prediction at LHC (3)
It is sensitive to the hot nuclear matter effect (thermalization
of charm quarks and regeneration in QGP), but it is almost
independent of the cold nuclear matter effect (shadowing) !
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Moving Heavy Quark Potential
lattice calculated free energy for
static heavy quarks
J/ψs are not at rest in the QGP!
what is the potential for moving
heavy quarks ?
The screening effect is due to the rearrangement of the
charged particles when a pair of heavy quarks (source) is
put into the medium.
When the source moves in the medium, it costs some time
for the screening charges to catch up with the source. This
delay of response reduces the screening charges around the
source and thus weakens the screening effect.
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Running Dissociation Temperature
A non-equilibrium problem, the transport equation for the
time dependent charge density
,
relaxation time
color conductivity from lattice simulation
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R_AA at High Pt
It seems no way to reach the large R_AA at high Pt,
if the dissociation temperature does not run!
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Conclusion
While the quarkonium yield behaves
similarly at SPS, RHIC and LHC, the
transverse momentum distribution is
sensitive to the nature of the medium
and can be used to signal the QGP
formation.
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