Partonic EoS at RHIC
Nu Xu
Nuclear Science Division
Lawrence Berkeley National Laboratory
Many Thanks to the Conference Organizers
Nu Xu
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Outline
1) Introduction
2) Hadron Spectra
3) Event anisotropy
4) Summary and outlook
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Physical Goals at RHIC
Identify and study the properties of
matter (EoS) with partonic degrees
of freedom and determine the QCD
phase diagram.
Penetrating probes
Bulk probes
- direct photons, leptons
- “jets” and heavy flavor
- spectra, v1, v2 …
Hydrodynamic
Flow
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=
- partonic collectivity
- fluctuations
Collectivity

Local
Thermalization
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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High-Energy Nuclear Collisions
jets, leptons
Initial Condition
- initial scatterings
- baryon transfer
- ET production
- parton dof
Q2
J/y, D
partonic scatterings?
early thermalization?
W
TC
Tch
f
X
System Evolves
- parton interaction
- parton/hadron
expansion
elliptic flow v2
L
p, K, K*
D, p
Bulk Freeze-out
- hadron dof
- interactions stop
radial flow bT
d, HBT
time
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
Tfo
4/27
Hadron Spectra from RHIC
p+p and Au+Au collisions at 200 GeV
ud
ss
uud
sss
more central collisions
0-5%
mT 
pT2  m 2
f  exp(mT /Tslope )
Multi-strange hadron spectra are exponential in their
shapes.
STAR white papers
 - Nucl. Phys. A757, 102(2005).
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Thermal Model Fits (Blast-Wave)
Source is assumed to be:
– Locally thermal equilibrated
– Boosted in radial direction
boosted
E.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993)
random
d 3N
(u p  )/T fo
E 3 e
pd  
dp

dN

mT dmT

R
0
  tanh 1 bT
 m cosh    p sinh  
rdrmT K1 T
I0  T

 Tfo
  Tfo 
 r 
bT  b S  
 R
  0.5, 1, 2
Extract thermal temperature Tfo and velocity parameter bT
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Blast Wave Fits: Tfo vs. bT
200GeV Au + Au collisions
1) p, K, and p change
smoothly from peripheral
to central collisions.
2) At the most central
collisions, bT reaches
0.6c.
3) Multi-strange particles f,
W are found at higher Tfo
and lower bT
 light hadrons move
with higher velocity
compared to strange
hadrons
STAR: NPA715, 458c(03); PRL 92,
112301(04); 92, 182301(04).
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Compare with Model Results
Hydro model works well for p, K, p, but over-predicts flow for multistrange hadrons
Initial ‘collective kick’ introduced (P. Kolb and R. Rapp, PRC67)
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Slope Parameter Systematics
mT  pT2  m 2 ;

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f exp(mT /Tslope )
Partonic expansion!
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Direct Radiation from the Matter
SPS energy
PRL (07)
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Low-mass Dileptons
ALEPH data: Vacuum
1) At s~1 GeV2, 2p
channel strength drop
2) Measured vector+(e+e-), but axial vector?
 Related to the collective
expanding?
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Direct Radiation from the Matter
Di-leptons allow us
to measure the direct
radiation from the
matter with partonic
degrees of freedom,
no hadronization!
Puzzle 1: dramatic
change of the slope
parameter at m ~ 1
GeV2
Puzzle 2: source of
T at m ≥ 1.5 GeV2
RHIC & LHC:
T will increase with
mass!
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Summary I
1) Multi-strange hadrons and heavy quark
hadrons freeze-out early
2) At RHIC, mass > 1 GeV2, partonic interactions
dominate. Interactions of pp, pN are important
for mass < 1 GeV2.
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Anisotropy Parameter v2
coordinate-space-anisotropy

momentum-space-anisotropy
y
x
 y2  x2
 2
 y  x2
v 2  cos2 ,   tan (
1
py
px
)
Initial/final conditions, EoS, degrees of freedom

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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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v2 - Identified Particles at High pT
pions
kaons
protons
QM08: S. Huang ; M. Issah
PHENIX results from their new MRPC-TOF and RP detectors!
Extended to higher pT region!
The more central the collision, the smaller the v2
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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v2 - High pT - nq Scaling
QM08: S. Huang ; M. Issah
1) Scaling observed at both centralities.
2) KET scaling seems break down for KET/nq > 1 GeV/c2 in
peripheral collisions - non-flow effects
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Collectivity, Deconfinement at RHIC
- v2 of light hadrons and
multi-strange hadrons
- scaling by the number of
quarks
At RHIC:
 mT - NQ scaling
 De-confinement
i
ii
PHENIX: PRL91, 182301(03)
STAR: PRL92, 052302(04), 95, 122301(05)
nucl-ex/0405022, QM05
S. Voloshin, NPA715, 379(03)
Models: Greco et al, PRC68, 034904(03)
Chen, Ko, nucl-th/0602025
Nonaka et al. PLB583, 73(04)
X. Dong, et al., Phys. Lett. B597, 328(04).
….
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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f -meson v2: Partonic Collectivity
QM08: J. Chen; X.B. Wang
“f-mesons are produced via coalescence of seemingly
thermalized quarks in central Au+Au collisions. This
observation implies hot and dense matter with partonic
collectivity has been formed at RHIC”
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Centrality Dependence of PID v2
QM08: Y. Lu; S Dash
 All centralities: mass ordering at low pT  mT-m scaling at low mT-m.
 All centralities: baryon v2 > meson v2 at intermediate pT and mT-m.
 Hydrodynamic model predictions do not show the scaling behavior.
Non-viscous hydro: P. Huovinen, private communications, 07/ / STAR data: arXiv:0801.3466v1
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Eccentricity Scaling(?)
STAR: arXiv:0801.3466v1
QM08: Y. Lu ; S Dash
200 GeV Au+Au
S. Voloshin, A. Poskanzer, PL B474, 27(00).
D. Teaney, et. al., nucl-th/0110037
 Larger v2/part indicates stronger flow in more central collisions.
 The observed nq-scaling does not necessarily mean
thermalization.
Nu Xu
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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(no) Scaling in Hydro Model
1) No scaling is observed
in the non-viscous
hydrodynamic model
predictions.
2) Realistic calculations
with viscosity are
necessary!
- STAR data: PRC 72, 014904, 2005
arXiv:0801.3466v1
- Non-viscous hydrodynamic results:
P. Huovinen, private communications
2007
- D. Teaney, J. Lauret, and E.Shuryak,
nucl-th/0110037
- T. Hirano et al. Phy. Lett. B636,
299 (06); J. Phys. G34 S879(07);
arXiv: 0710.5795
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Summary II
1) Partonic interactions are responsible to
early collectivity
 Partonic Collectivity at RHIC.
2) More sophisticated, serious model
calculations, including proper initial condition,
viscosity, … are needed.
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Quark Masses
1)
2)
Higgs mass: electro-weak
symmetry breaking. (current
quark mass)
QCD mass: Chiral symmetry
breaking. (constituent quark
mass)
 New mass scale compared
to the excitation of the
system.
 Important tool for studying
properties of the hot/dense
medium at RHIC.
Total quark mass (MeV)
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 Test pQCD predictions at
RHIC.
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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New Results on Non-photonic e v2
PHENIX run-IV:
PRL, 98, 172301 (2007)
QM08: R. Averbeck; A. Dion
1) Heavy quark collectivity => light quark thermalization!
Muller nucl-th/0404015
2) Non-photonic electron v2 indicates non-zero v2 of Charm-hadrons.
3) Large systematic errors.
Need directly reconstructed heavy quark-hadrons!!
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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STAR Detector
MRPC ToF barrel
MTD
EMC barrel
EMC End Cap
RPSD
FMS
Fp0S
PMD
- DAQ1000
- TPC FEE
finished
HFT: Si-pixels; IST: Si-strips; FGT: GEM-layers
ongoing
Integrated Tracking Upgrades
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- MTD
- Soft 
“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Charm Hadron v2
D0, D±, D*,Ds
LC
Bottom-hadrons
Charm background
At low mass region
- 200 GeV Au+Au minimum biased collisions (500M events).
- Charm collectivity  drag/diffusion constants  medium properties!
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“Hot and Dense Matter in the RHIC-LHC Era”, Mumbai, India, February 12-14, 2008
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Summary
Physics Today
L. McLerran, T. Ludlam,
Hot and dense system created in
Au+Au collisions At RHIC
Spectra: At RHIC, mass > 1 GeV2,
partonic interactions dominate.
Anisotropy v2: Partonic interactions
are responsible to early collectivity at
RHIC.
More sophisticated, serious model
calculations are needed.
Next Step:
Test thermalization of light-quark
by studying the heavy-quark
collectivity.
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