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Multi-Parton Dynamics at RHIC

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

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Multi-Parton Dynamics at RHIC

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  1. Multi-Parton Dynamics at RHIC Huan Zhong Huang Department of Physics and Astronomy University of California Los Angeles @ShanDong University Oct. 17 2003

  2. Outline • Experimental Observations at Intermediate pT • Multi-parton Dynamics -- coalescence/recombination picture -- possible gluon junction interaction • Hydrodynamics and pQCD • Mass Dependence in Cronin Effect • Outlook

  3. Volcanic mediate pT – Spatter (clumps) Intermediate pT Region

  4. coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, dof, EOS Elliptic Flow Parameter v2

  5. y Small expansion velocity Collective Pressure High pressure gradient Large expansion velocity pT dependent ! Low particle density Surface Geometrical Phase Space Surface Emission Pattern High particle density pT independent ! or pT dependence may come from surface thickness (pT) Dynamical Origin of Elliptic Flow STAR Preliminary Au+Au 200 GeV x V2 in the intermediate pT region: Dynamics for Saturation ? Particle Dependence of v2 ?

  6. What Determines the pT Dependence ? v2 Charged hadron elliptic flow Particle production steep func of pT V2 little pT dependence 2<pT<5 GeV/c

  7. STAR PHENIX What Determines the Particle Dependence ? Baryon Meson Why saturation at intermediate pT ? Why baryon and meson difference ?

  8. 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.

  9. [yield/N-N]central RCP= [yield/N-N]peripheral What Determines the Baryon-Meson Yield? RCP ~ 1 particle production proportional to the number of binary nucleon-nucleon collisions – superposition of independent of n-n collisions. Intermediate pT region special !!

  10. less opaque: more particles more opaque: fewer particles Surface Model Alone Does not Work Neither Woods-Saxon nor Hard-Sphere distribution can match the v2 magnitude readily with standard fragmentation for particle formation !

  11. Multi-Parton Dynamics STAR+PHENIX Hadronization Scheme for Bulk Partonic Matter: • 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 ! Quark Coalescence – (ALCOR-J.Zimanyi et al, AMPT-Lin et al, Molnar+Voloshin …..) Quark Recombination – (R.J. Fries et al….)

  12. [yield/N-N]central RCP= [yield/N-N]peripheral Nuclear Modification Factor RAA RCP RCP Multi-parton dynamics predict baryon yield increases with centrality FASTER than mesons! Yield ~ rn and nL>nK  a feature not present in single parton fragmentation ! Multi-parton dynamics: coalescence, recombination and gluon junctions.

  13. Strangeness from Bulk Partonic Matter Strangeness enhancement is most prominent at intermediate pT from quark coalescence in an equilibrated bulk matter ! L X W

  14. 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

  15. Interesting Measurements hydro • L X W at high pT !! Open Charm !! • STAR TOF Upgrade ! C. Nonaka et al nucl-th/0308051

  16. 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!

  17. @mid-rapidity Pb+Pb @SPS Many more Ws Than Ws !! The W to W Ratio

  18. Scenarios of Baryon Number Transport Direct Transport Through Gluon Junctions … W + K + K + K + (X) Indirect Transport Through Pair Production Modified by Baryon Chemical Potential … • W and W X K • X and X (L / S) K • L and L (p / n ) K Net Baryon Density Increases the Associated Production and Transfers net baryon number to multiply-strange baryons !

  19. q q Anti-Baryon Baryon q q q q Multi-parton Dynamics and Baryon Production Baryon (Hyperon) Production may be Enhanced by Gluon-Junction Interaction Dynamics: Gluon Junction Mechanism -- (Kharzeev, Gyulassy and Vance ….) Junction Measure local baryon and anti-baryon quantum number correlations in DpT-Dy space ! Event-by-Event STAR Hyperon Correlations Doable with STAR TOF and SVT Upgrade !

  20. Hydrodynamics at Intermediate pT? Hydrodynamics fails at intermediate pT no v2 saturation Particle dependence of v2 and RAA(RCP) • At intermediate pT, RCP of K0S is lower than that of Lambda • Hydro/p-QCD: mass effect • Quark coalescence: Particle type effect • Need f!!! • RCP of f close to that of K0S other than that of Lambda • Particle production at intermediate pT region is driven by the particle’s type, not the mass Higher statistics f data from d+Au is being analyzed by Xiangzhou Cai from SINR. Future Au+Au data + TOF upgrade !!

  21. p+ p- RW/Be K+ K- p p Particle Dependence in Cronin Effect Significant at Low Energy 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.B. Straub et al., PRL 68 452 (1992) p+A collisions at sqrt(s) = 38.8 GeV

  22. Traditional Cronin Effect is not the whole story at RHIC STAR d+Au from TOFr analysis (USTC+BNL+RICE) Results on KS, L and f will reach higher pT (SINR+UCLA)

  23. Nuclear Modification Factor Rcp • At intermediate pT, RCP of K0S is lower than that of Lambda • p-QCD: mass effect • Quark coalescence: Particle type effect • RCP of f is closer to K0S than Lambda • Particle production at intermediate pT region is dividing by the particle’s type, not the mass STAR Preliminary 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 Xiangzhou Cai

  24. 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 !! (f, L, X, W, J/y, and D mesons) STAR TOF/microSVT detector upgrade essential !

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