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Multi-Parton Dynamics at RHIC. Huan Zhong Huang Department of Physics and Astronomy University of California Los Angeles @ShanDong University Oct. 17 2003. Outline. Experimental Observations at Intermediate p T Multi-parton Dynamics -- coalescence/recombination picture - PowerPoint PPT Presentation
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Multi-Parton Dynamics at RHIC
Huan Zhong Huang
Department of Physics and Astronomy
University of California Los Angeles
@ShanDong University
Oct. 17 2003
Outline
1) Experimental Observations at Intermediate pT
2) Multi-parton Dynamics
-- coalescence/recombination picture
-- possible gluon junction interaction
3) Hydrodynamics and pQCD
4) Mass Dependence in Cronin Effect
5) Outlook
Intermediate pT Region
Volcanic mediate pT – Spatter (clumps)
Elliptic Flow Parameter v2
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Initial/final conditions, dof, EOS
1i
Ritttt
))ψcos(i(2v1dydpp
dN
2π
1
dyddpp
dN
y
Dynamical Origin of Elliptic Flow
STAR PreliminaryAu+Au 200 GeV
V2 in the intermediate pT region: Dynamics for Saturation ? Particle Dependence of v2 ?
Collective Pressure
High pressure gradientLarge expansion velocity
Small expansion velocity
pT dependent !
Surface Geometrical Phase Space
Surface Emission PatternHigh particle density
Low particle density
pT independent ! orpT dependence may comefrom surface thickness (pT)
x
What Determines the pT Dependence ?
v2
Particle production steep func of pT
V2 little pT dependence 2<pT<5 GeV/c
Charged hadron elliptic flow
STAR
PHENIX
What Determines the Particle Dependence ?
Baryon
Meson
Why saturation at intermediate pT ?Why baryon and meson difference ?
So Many Baryons !!
•Two component shape evident in the KS spectra.
•The Λ yield exceeds the KS yield at intermediate pT.
•The Λ yield is most enhanced in central collision.
What Determines the Baryon-Meson Yield?
RCP=[yield/N-N]central
[yield/N-N]peripheral
RCP ~ 1 particle production proportional to the number of binary nucleon-nucleon collisions – superposition of independent of n-n collisions.
Intermediate pT region special !!
Surface Model Alone Does not Work
more opaque:fewer
particles
less opaque:more particles
Neither Woods-Saxon nor Hard-Sphere distribution canmatch the v2 magnitude readily with standard fragmentation for particle formation !
Multi-Parton Dynamics
KS – two quark coalescence– three quark coalescence from the partonic matter surface?!
Particle v2 may be related to quark matter anisotropy !!
pT < 1 GeV/c may be affected by hydrodynamic flow !
Hadronization Scheme for Bulk Partonic Matter:
Quark Coalescence – (ALCOR-J.Zimanyi et al, AMPT-Lin et al,Molnar+Voloshin …..)
Quark Recombination – (R.J. Fries et al….)
STAR+PHENIX
Nuclear Modification Factor RAA RCP
Multi-parton dynamics predict baryon yield increases with centrality FASTER than mesons! Yield ~ n and n>nK a feature not present in single parton fragmentation !
Multi-parton dynamics: coalescence, recombination and gluon junctions.
RCP
RCP=[yield/N-N]central
[yield/N-N]peripheral
Strangeness from Bulk Partonic Matter
Strangeness enhancement is most prominent at intermediate pT from quark coalescence in an equilibrated bulk matter !
Recombination versus Coalescence
Standard Fragmentation Scheme – leading parton fragments into hadrons quarks from pair production out of vacuum.
Recombination Model -- R. Hwa et al … original recombination idea -- Recent Fries et al… for heavy ion collisions leading parton from pQCD processes recombined with soft partons from thermalized quarks/gluons.
Coalescence Model thermalized quarks (gluons) coalescence form hadrons.
Flavor Correlations and Dynamical Transition
Interesting Measurements
C. Nonaka et al nucl-th/0308051
hydro
at high pT !!Open Charm !!STAR TOF Upgrade !
Intermediate pT Dynamics
• Identified particle spectra and elliptic flow at intermediate pT are unique probes of multi-parton dynamics for particle formation – clustering of quarks!
• Strangeness equilibration of the bulk partonic matter may also reflect in the enhanced strange baryon production from quark clusterings.
The dynamics at the intermediate pT can be the key to a phenomenological hadronization description of bulk partonic matter!
The to Ratio
@mid-rapidityPb+Pb @SPSMany more sThan s !!
Scenarios of Baryon Number Transport
Direct Transport Through Gluon Junctions …
X)
Indirect Transport Through Pair Production Modified by Baryon Chemical Potential …
and K
and K
and p / n ) K
Net Baryon Density Increases the Associated Production and Transfers net baryon number to multiply-strange baryons !
Multi-parton Dynamics and Baryon Production
q
q
q q
Baryon Anti-Baryon
Baryon (Hyperon) Production may be Enhanced by Gluon-Junction Interaction Dynamics:
Gluon Junction Mechanism -- (Kharzeev, Gyulassy and Vance ….)
Junction
Event-by-Event STAR Hyperon Correlations Doable with STAR TOF and SVT Upgrade !
Measure local baryon and anti-baryon quantum number correlations in pT-y space !
Hydrodynamics at Intermediate pT?
At intermediate pT, RCP of K0S is
lower than that of LambdaHydro/p-QCD: mass effectQuark coalescence: Particle type effectNeed !!!
RCP of close to that of K0S other
than that of LambdaParticle production at intermediate pT region is driven by the particle’s type, not the mass
Hydrodynamics fails at intermediate pT
no v2 saturation Particle dependence of v2 and RAA(RCP)
Higher statistics data from d+Au is being analyzed by Xiangzhou Cai from SINR.Future Au+Au data + TOF upgrade !!
Particle Dependence in Cronin Effect Significant at Low Energy
P.B. Straub et al., PRL 68 452 (1992)p+A collisions at sqrt(s) = 38.8 GeV
Strong particle dependence proton > kaon > pion
No significant particle and anti-particle difference ! no valence quark effect ! The Cronin effect is expected to decrease with beam energy !
p p
K+ K-
RW/Be
Traditional Cronin Effect is not the whole story at RHIC
STAR d+Au from TOFr analysis (USTC+BNL+RICE)Results on KS, and will reach higher pT (SINR+UCLA)
Nuclear Modification Factor Rcp
At intermediate pT, RCP of K0
S is lower than that of Lambda
p-QCD: mass effectQuark coalescence: Particle type effect
RCP of is closer to K0S
than LambdaParticle production at intermediate pT region is dividing by the particle’s type, not the mass
The ratio of central (top 20%) over peripheral (100-40%) (RCP) normalized by <Nbin>, vs. transverse momentum. <Nbin>|cent=14.18; <Nbin>|periph=3.34
STAR Preliminary
Xiangzhou Cai
Outlook
Intermediate pT very special !!
Multi-parton dynamics --- coalescence --- recombinations --- gluon junction interactions
Hadronization phenomenology of bulk partonic matter
Particle dependence of Cronin effect
Identified Particle Spectra and Elliptic Flow !!(J/, and D mesons) STAR TOF/microSVT detector upgrade essential !
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