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Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 1 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//Collective Expansion inCollective Expansion in Relativistic Heavy Ion Collisions Relativistic Heavy Ion Collisions
-- Search for the partonic EOS at RHIC-- Search for the partonic EOS at RHIC
Nu Xu
Lawrence Berkeley National Laboratory
Many Thanks to Organizers!Many Thanks to Organizers!J. Castillo, X. Dong, H. Huang, H.G. Ritter, K. Schweda, P. Sorensen, Z. Xu
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 2 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
OutlineOutline
Introduction
Energy loss - QCD at work
Bulk properties - ∂PQCD
- hadron spectra- elliptic flow v2
Summary and Outlook
http://www4.rcf.bnl.gov/brahms/WWW/brahms.html http://www.phobos.bnl.gov/ http://www.phenix.bnl.gov/ http://www.star.bnl.gov/
Wei Hai, China, 2004Wei Hai, China, 2004
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PPhase diagram of strongly hase diagram of strongly interacting matterinteracting matter
CERN-SPS, RHIC, LHC: high temperature, low baryon density
AGS, GSI (SIS200): moderate temperature, high baryon density
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 4 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Study of Nuclear Collisions Like…Study of Nuclear Collisions Like…P.C. Sereno et al. Science, Nov. 13, 1298(1998). (Spinosaurid)
Bulk Bulk PropertiesProperties
High pHigh pTT - -
QCD probesQCD probes
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 5 / 34
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PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
High-energy Nuclear CollisionsHigh-energy Nuclear CollisionsS
. B
ass
Experimental approaches:
1) Energy loss - ‘jet-quenching’2) Elliptic flow - v2, radial flow3) Heavy flavor production, combination of 1) and 2)
Hadronization and Freeze-out
Initial conditions
(1) Initial condition in high-energy nuclear collisions(2) Cold-QCD-matter, small-x, high-parton density
- parton structures in nucleon / nucleus
Parton matter - QGP- The hot-QCD
Initial high Q2 interactions
(1) Hard scattering production - QCD prediction(2) Interactions with medium - deconfinement/thermalization(3) Initial parton density
time
Wei Hai, China, 2004Wei Hai, China, 2004
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//Talk/2004/07USTC04/NXU_USTC_8July04//
High-energy Nuclear CollisionsHigh-energy Nuclear Collisions
Initial Condition - initial scatterings - baryon transfer - ET production - parton dof
System Evolves - parton interaction - parton/hadron expansion
Bulk Freeze-out - hadron dof - interactions stop
jets
J/D
K, K*
p
d, HBT
elliptic flow velliptic flow v22
radial radial flowflowTT
Q2
time
partonic scatterings?early thermalization?
TTCC
TTchch
TTfofo
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 7 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Identify and study the properties of matter 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) > 3 GeV/c) collectivity - collective motion of observed hadrons, not necessarily reached
thermalization among them.
Physics Goals at RHIC
HydrodynamicFlow
CollectivityLocal
Thermalization=
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 8 / 34
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Collision Geometry
x
z
Non-central Collisions
Number of participants: number of incoming nucleons in the overlap regionNumber of binary collisions: number of inelastic nucleon-nucleon collisions
Charged particle multiplicity collision centralityReaction plane: x-z plane
Au + Au sNN = 200 GeV
beam
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 9 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Au + Au Collisions at RHICAu + Au Collisions at RHIC
STARSTAR
Central Event
(real-time Level 3)
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 10 / 34
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Charged Hadron Density19.6 GeV 130 GeV 200 GeV
Charged hadron pseudo-rapidity
1) High number of Nch indicates initial high density;2) Mid-y, Nch Npart nuclear collisions are not incoherent;3) Saturation model works
Initial high parton density at RHICPRL 85, 3100 (00); 91, 052303 (03); 88, 22302(02); 91,
052303 (03)
PHOBOS Collaboration
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 11 / 34
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Energy Loss in A+A Collisions
σddpd
ddpNd
TpR
TNN
TAA
AATAA /
/1)(
2
2
=
Nuclear Modification Factor:
back-to-back jets disappear
leading particle suppressed
p+p Au + Au
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 12 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Hadron Suppression at RHIC
Hadron suppression in more central Au+Au collisions!
Wei Hai, China, 2004Wei Hai, China, 2004
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Jets Observation at RHIC
p+p collisions at RHICJet like events observed
Au+Au collisions at RHICJets?
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 14 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Suppression and Correlation
In central Au+Au collisions: hadrons are suppressed and back-to-back ‘jets’ are disappeared. Different from p+p and d+Au collisions.
Energy density at RHIC: > 5 GeV/fm3 ~ 300
Parton energy loss: Bjorken 1982(“Jet quenching”) Gyulassy & Wang 1992…
Wei Hai, China, 2004Wei Hai, China, 2004
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Energy Loss and Equilibrium
Leading hadrons
Medium
In Au +Au collision at RHIC: - Suppression at the intermediate pT region - energy loss
- The energy loss leads to progressive equilibrium in Au+Au collisions STAR: nucl-ex/0404010
Wei Hai, China, 2004Wei Hai, China, 2004
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Parton Energy Loss
(1) Measured spectra show evidence of suppression up to pT ~ 6 GeV/c; (2) Jet-like behavior observed in correlations: - hard scatterings in AA collisions
- disappearance of back-to-back correlations
“Partonic” Energy loss process leads to progressive equilibrium in the medium
Next step: fix the partonic Equation of State, bulk properties
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 17 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Pressure, Flow, …
ddσσ = dU + pdV = dU + pdV σ– entropy; p – pressure; U – energy; V – volume
= kBT, thermal energy per dof
In high-energy nuclear collisions, interaction among constituents and density distribution will lead to: pressure gradient pressure gradient collective flow collective flow
number of degrees of freedom (dof) Equation of State (EOS) No thermalization is needed – pressure gradient only depends on the density gradient and interactions. Space-time-momentum correlations!
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 18 / 34
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Transverse Flow Observables
As a function of particle mass:• Directed flow (v1) – early• Elliptic flow (v2) – early• Radial flow – integrated over whole evolution
Note on collectivity:1) Effect of collectivity is accumulative – final effect is the sum of all processes. 2) Thermalization is not needed to develop collectivity - pressure gradient depends on density gradient and interactions.
€
dNptdptdyd
= 12
dNptdptdy
1+ 2vi (cos i )i=1
∑⎡
⎣⎢
⎤
⎦⎥
pt = px2 +py
2 , mt = pt2 +m2
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 19 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Hadron Spectra From RHICHadron Spectra From RHICmid-rapidity, p+p and Au+Au collisions at 200 GeVmid-rapidity, p+p and Au+Au collisions at 200 GeV
ce nt ral ity5%
10-20%
20-40%
40-60%
60-80%
€
mT = pT2 + m2
Results from BRAHMS, PHENIX, and STAR experiments
(sss)(ssd)(usd)
(ss)
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 20 / 34
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Compare with Model Results
Model results fit to , K, p spectra well, but over predicted <pT> for multi-strange hadrons - Do they freeze-out earlier?
Phys. Rev. C69 034909 (04); Phys. Rev. Lett. 92, 112301(04); 92, 182301(04); P. Kolb et al., Phys. Rev. C67 044903(03)
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 21 / 34
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Thermal fits: Tfo vs. < >
1) 1) , , KK, and , and pp change change smoothly from peripheral smoothly from peripheral to central collisions.to central collisions.
2) At the most central2) At the most central collisions, <collisions, <TT> reaches> reaches
0.6c.0.6c.
3) Multi-strange particles 3) Multi-strange particles ,, are found at higher Tare found at higher Tfofo
(T~T(T~Tchch) and lower <) and lower <TT>>
Sensitive to early Sensitive to early partonic stage!partonic stage!
How about vHow about v22??
STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04).
200GeV Au + Au collisions200GeV Au + Au collisions
Chemical Freeze-out: inelastic interactions stopKinetic Freeze-out: elastic interactions stop
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 22 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Anisotropy Parameter vAnisotropy Parameter v22
€
=⟨y 2 − x 2⟩⟨y 2 + x 2⟩
v2 = cos2ϕ , ϕ = tan−1(pypx
)
Initial/final conditions, EoS, degrees of freedom
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 23 / 34
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v2 at Low pT
- At low pT, hydrodynamic model fits well for minimum bias events indicating early thermalization in Au+Au collisions at RHIC!- More theory work needed to understand details: such as centrality dependence of v2; consistency between spectra and v2 …
P. H
uo
vi ne
n, p
r ivate
com
mu
nica
t i on
s, 20
04
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 24 / 34
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v2 at All pT
v2, the spectra of multi-strange hadrons, and thescaling of the number ofconstituent quarks
Partonic collectivity has been attained at RHIC! Deconfinement, model dependently, has been attained at RHIC!
Next question is thethermalization of lightflavors at RHIC:- v2 of charm hadrons- J/ distributions !!
PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04)Models: R. Fries et al, PRC68, 044902(03), Hwa, nucl-th/0406072
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 25 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Nuclear Modification Factor
)/(
)/()(
2
2
dydpNNd
dydpNNdpR
Tperipheralbinary
peripheral
Tcentralbinary
central
TCP = 1) Baryon vs. meson effect!
2) Hadronization via coalescence
3) Parton thermalization (model) - (K0, ): PRL92, 052303(04); NPA715, 466c(03); - R. Fries et al, PRC68, 044902(03)
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 26 / 34
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Bulk Freeze-out Systematics
The additional increase in T is likely due to partonic pressureat RHIC.
1) v2 self-quenching, hydrodynamic model works at low pT
2) Multi-strange hadron freeze-out earlier, Tfo~ Tch
3) Multi-strang hadron show strong v2
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 27 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Partonic Collectivity at RHIC
1) Copiously produced hadrons freeze-out: Tfo = 100 MeV, T = 0.6 (c) > T(SPS)
2)* Multi-strange hadrons freeze-out: Tfo = 160-170 MeV (~ Tch), T = 0.4 (c)
3)** Multi-strange v2: Multi-strange hadrons and flow!
4)*** Constituent Quark scaling: Seems to work for v2 and RAA (RCP)
Partonic (u,d,s) collectivity at RHIC!
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 28 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
Summary & OutlookSummary & Outlook
(1) Charged multiplicity - high initial density
(2) Parton energy loss - QCD at work
(3) Collectivity - pressure gradient ∂PQCD
Deconfinement and Partonic collectivity
Open issues - partonic (u,d,s) thermalization - heavy flavor v2 and spectra - di-lepton and thermal photon spectra
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 29 / 34
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Equation of State
€
∂μTμν = 0
∂μ jμ = 0 j μ (x) = n(x)uμ (x)
T μν = ε(x) + p(x)[ ]uμuν − gμν ∗p(x)
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
lat=1.15 GeV/fm3
P. Kolb et al., Phys. Rev. C62, 054909 (2000).
With given degrees of freedom, the EOS - the system response to the changes of the thermal condition - is fixed by its p and T or .
Energy density GeV/fm3
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 30 / 34
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CERN-SPS, RHIC, LHC: high temperature, low baryon density
AGS, GSI (SIS200): moderate temperature, high baryon density
PPhase diagram of strongly hase diagram of strongly interacting matterinteracting matter
GSIGSI
RHICRHICLHCLHC
Wei Hai, China, 2004Wei Hai, China, 2004
Nu Xu 31 / 34
//Talk/2004/07USTC04/NXU_USTC_8July04//
RHIC @ Brookhaven National LaboratoryRHIC @ Brookhaven National Laboratory
h
STAR
PHENIX
PHOBOS
BRAHMS
Wei Hai, China, 2004Wei Hai, China, 2004
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Experiments @ LHCExperiments @ LHC
Wei Hai, China, 2004Wei Hai, China, 2004
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ALICE: dedicated HI experimentCMS: pp experiment with HI program
Wei Hai, China, 2004Wei Hai, China, 2004
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Structure of Nuclei far from Stability
Antiproton storage ring:Hadron Spectroscopy
Compressed Baryonic Matter
Ion and Laser Induced Plasmas:
High Energy Density in Matter
Key features: Intense, high-quality secondary beams of rare isotopes and antiprotons
2012: first beam$$$$: ~ 109 Euro
International Accelerator Facility forBeams of Ions and Antiprotons at Darmstadt
Polarized anti-proton proton collisions, nucleon structure
SIS 100 Tm
SIS 200 (250) Tm
23 (29) AGeV U
60 (75) GeV p