Partonic EoS in HighEnergy Nuclear Collisions

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Partonic EoS inHigh-Energy Nuclear
Collisions
Nu XuLawrence Berkeley National
Laboratory Many thanks to the symposium
organizers
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Outline

• Numbers about Nu Xu
• Date of birth 5 (Henning Index)
• Ph.D 1985 - 1990 Stony Brook
• Postdoc 1990 - 1994 Stony Brook
• .
• HI 5

work uncertain
work question
work doubt
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Outline

• Introduction
• - equation of state
• - collectivity, local thermalization
• - chemical freeze-out QCD phase diagram
• Jet-quenching at RHIC
• Bulk properties
• - partonic collectivity from multi-strange
  hadrons
• - hint of charm collectivity
• Summary

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QCD Phase Diagram
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LGT Predictions

• 1) Large increase in ?
• a fast cross cover !
• 2) Does not reach ideal,
• non-interaction S. Boltzmann
• limit !
• many body interactions
• Collective modes
• Quasi-particles are necessary
• 3) TC 170 MeV robust!
• Z. Fodor et al, JHEP 0203014(02)
• Z. Fodor et al, hep-lat/0204001
• C.R. Allton et al, hep-lat/0204010
• F. Karsch, Nucl. Phys. A698, 199c(02).

Lattice calculations predict TC 170 MeV
Strongly interacting quark-gluon Plasma - sQGP
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Physical Goals at RHIC
Identify and study the properties of matter
(EOS) with partonic degrees of freedom.
Penetrating probes Bulk probes -
direct photons, leptons - spectra, v1,
v2 - jets and heavy flavor
- partonic collectivity -
fluctuations jets - observed
high pT hadrons (at RHIC, pT(min) gt 3 GeV/c)
collectivity - collective motion of observed
hadrons, not necessarily reached
thermalization among them.
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STAR
AuAu/CuCu/dAu 200 GeV QGP pp
(polarized) 200/500 GeV ?g
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STAR TPC
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Au Au Collisions at 130 GeV
Central Event
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Collision Geometry, Flow
z
x
Non-central Collisions
Number of participants number of incoming
nucleons in the overlap region Number of binary
collisions number of inelastic nucleon-nucleon
collisions Charged particle multiplicity ?
collision centrality Reaction plane x-z plane
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Hadron Spectra from RHICpp and AuAu collisions
at 200 GeV
0-5
more central collisions
Multi-strange hadron spectra are exponential in
their shapes.
STAR white papers - Nucl.
Phys. A757, 102(2005).
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Yields Ratio Results

• In central collisions, thermal model fit well
  with ?S 1. The system is thermalized at RHIC.
• Short-lived resonances show deviations. There is
  life after chemical freeze-out. RHIC
  white papers - 2005, Nucl. Phys. A757, STAR
  p102 PHENIX p184.
• First paper PBM et al, Phys. Lett. B344,
  43(95).

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QCD Phase Diagram
First paper PBM et al, Phys. Lett. B344,
43(95).
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EOS Study Step I

• In Au Au collisions
• Hadron yields in the state of equilibrium -
  chemical freeze-out near the phase transition
  temperature
• Step I probing the medium with hard
  interactions

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Energy Loss in AA Collisions
leading particle suppressed
back-to-back jets disappear
pp Au Au
Nuclear Modification Factor
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Jet-Quenching at RHIC
In central AuAu collisions hadrons are
suppressed and back-to-back jets disappear.
Different from pp and dAu collisions. Energy
density at RHIC ? gt 5 GeV/fm3 30?0 Parton
energy loss Bjorken 1982 (Jet
quenching) Gyulassy Wang 1992
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Jet-like di-hadron Correlations
New results, year-4

• Larger data sample (year-4)
• allows analysis at higher pT
• Emergence of the away side peak
• Background negligible at higher pT,assoc
• - quantify the amount of suppression. Tests the
  medium property
• STAR Preliminary, QM05

8 lt pT,trig lt 15 GeV
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Heavy Flavor Hadron Energy Loss
1) Non-photonic electrons decayed from - charm
and beauty hadrons 2) At pT 6
GeV/c, RAA(n.e.) RAA(h) contradicts to naïve
pQCD predictions
Partonic energy loss - strongly interacting
matter produced at RHIC! Energy loss mechanism
under study M. Gyulassy et al. Problem
isolation of Charm hadron contributions from
Beauty-hadrons
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Hard-soft Interactions - Thermalization
Two sources of particles - hard hard scattering
products. - soft bulk medium constituents. -
Very different as seen in peripheral. Become
similar in central.
STAR, nucl-ex/0501016 / PRL 95, 120301(05).
near
ltpTgt (GeV/c)
Leading hadrons
from away-jets
away
Medium
from medium
- PID correlation analysis - Search for signal of
shock-wave.
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EOS Study Step II

• In Au Au collisions
• Hadron yields in the state of equilibrium -
  chemical freeze-out near the phase transition
  temperature
• (2) Partonic energy loss - tense
  interactions amongst partons, strongly
  interacting matter
• Step II study bulk properties with collective
  observations

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Equation of State / Hydrodynamics
Energy density ? GeV/fm3
EOS - the system response to the changes of the
thermal conditions - is fixed by its p and T (?).

• Equation of state
• EOS I relativistic ideal gas p ?/3
• EOS H resonance gas p ?/6
• EOS Q Maxwell construction
• Tcrit 165 MeV, B1/4 0.23 GeV
• ?lat1.15 GeV/fm3
• P. Kolb et al., Phys. Rev. C62,
  054909 (2000).

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Anisotropy Parameter v2
coordinate-space-anisotropy ?
momentum-space-anisotropy
y
py
x
px
Initial/final conditions, EoS, degrees of freedom
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High-Energy Nuclear Collisions

• jets
• J/y, D
• W
• f
• X
• L
• p, K, K
• D, p
• d, HBT

partonic scatterings? early thermalization?
Initial Condition - initial scatterings -
baryon transfer - ET production - parton
dof System Evolves - parton interaction -
parton/hadron expansion Bulk Freeze-out -
hadron dof - interactions stop
Q2
TC Tch Tfo
elliptic flow v2

radial flow bT
time
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v2 at Low pT Region
P. Huovinen, private communications, 2004

• Minimum bias data! At low pT, model result
  fits mass hierarchy well!
• - Details does not work, need more flow in the
  model!

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? -mesons Flow Partonic Flow

• ?-mesons are very special
• they do not re-interact in hadronic environment
• they are formed via coalescence with thermal
  s-quarks
• they show strong collective flow
• 
  STAR
  Preliminary QM05, M. Lemont, S. Blyth talks

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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
• ? Partonic Collectivity
• ? Deconfinement
• 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

i ii
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Hadronic Transport Model Results
uRQMD results show the particle type dependence
although the absolute amplitudes of v2 are a
factor of 2 or so too small! 1) At low pT
region mass ordering - feature of hydrodynamic
motion 2) Hadron type dependence at the
intermediate pT region - vacuum hadronic cross
sections used in the model.
Y. Lu et al., nucl-th/0602009
The observation of the NQ-scaling is unique, but
the explanation may not be!
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Multi-strange Hadron Ratios
In heavy ion collisions at RHIC, up to pT 4
GeV/c, (model predicts 8 GeV/c) the strangeness
production is dominated by the thermal like
processes. Hwa and
Yang, nucl-th/0602024 STAR data QM05, SQM06
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Thermal Model Fits

• Source is assumed to be
• Locally thermal equilibrated
• Boosted radially

boosted
E.Schnedermann, J.Sollfrank, and U.Heinz, Phys.
Rev. C48, 2462(1993)
random
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Blast Wave Fits Tfo vs. lt bT gt

• 1) p, K, and p change
• smoothly from peripheral
• to central collisions.
• 2) At the most central
• collisions, ??T? reaches
• 0.6c.
• 3) Multi-strange particles ?,
• ? are found at higher T
• and lower ??T?
• ? Sensitive to early partonic stage!
• STAR NPA715, 458c(03) PRL 92, 112301(04) 92,
  182301(04).

200GeV Au Au collisions
Multi-strange hadrons freeze-out with higher Tfo
(Tch) and smaller ??T?
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T vs. Mass Plot (SPS)

• Interaction with hadronic gas
• Large X-section limit
• pions, kaons, protons
• Small X-section limit
• ?, ?, J/ ?

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Slope Parameter Systematics
At RHIC, ?, ?, ?, and J/? show collective motion
in 200 GeV Au Au central collisions!

PHENIX (?, K, p, J/?) PRC69, 034909(04), QM05
STAR (?, ?, ?) QM05.
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EOS Parameters at RHIC
In central AuAu collisions at RHIC -
partonic freeze-out Tpfo 165 10 MeV
weak centrality dependence vpfo 0.2 (c) -
hadronic freeze-out Tfo 100 5 (MeV)
strong centrality dependence vfo 0.6 0.05
(c) Systematic study are needed to understand
the centrality dependence of the EOS
parameters Thermalization assumed
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EOS Study Step III

• In Au Au collisions
• Hadron yields in the state of equilibrium -
  chemical freeze-out near the phase transition
  temperature
• (2) Partonic energy loss - tense
  interactions amongst partons, strongly
  interacting matter
• (3) Partonic collectivity and
  de-confinement
• Step III test thermalization with heavy flavor
  hadrons

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Open-/Closed-charm Hadron Yields
A. Andronic, P. Braun-Munzinger, K. Redlich, J.
Stachel, Phys.Lett. B571 , 36(03).
T. Matsui and H. Satz, Phys. Lett. B178,
416(1996). L. Grandchamp and R. Rapp, Phys. Lett.
B523 , 60(01).
RHIC
RHIC
(1) open charm cross sections (3) medium
effects (? properties) (2) direct pQCD
production (4) absorption (color
screening) Model results are different,
centrality dependence measurements are important!
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Charm Cross Section Results
First set of measurements, systematic errors are
large. Precision data are needed - energy loss
analysis ? test pQCD in hot and dense medium -
J/? analysis ? test Charm thermalization and
de-confinement
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QCD Phase Diagram
phase boundary? (hadronic shore)
deep partonic ocean
LHC RHIC-II
RHIC energy scan CBM at GSI
Tpfo 16510 MeV vpfo 0.2 (c)
Tfo 1005 MeV vfo 0.60.05 (c)
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WORK

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