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Partonic Collectivity at RHIC ShuSu Shi for the STAR collaboration Lawrence Berkeley National Laboratory Central China Normal University
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DNP 2009, Oct. 13-17, Hawaii2 Introduction STAR Detectors v 2 Results and Discussions System size and Energy Dependence Multi-strange Hadron and Ω Summary Outline
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DNP 2009, Oct. 13-17, Hawaii3 T < T conf T > T conf constant potential linear potential r V(r,T) The potential between quarks is a function of distance. It also depends on the temperature. At low temperature, the potential increases linearly with the distance between quarks quarks are confined At high temperature (RHIC), the confinement potential is ‘melted’ quarks are deconfined Introduction
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DNP 2009, Oct. 13-17, Hawaii4 Elliptic Flow (v 2 ) Coordinate-Space Anisotropy Momentum-Space Anisotropy Strange hadron: less sensitive to late hadronic rescattering Elliptic flow => Early stage collision dynamics Good probe of the early stage of the collision partonic hadronic D , Ω, Ξ, Λ , K, p interactions
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DNP 2009, Oct. 13-17, Hawaii5 TPC dE/dx PID: pion/kaon: p T ~ 0.6 GeV/c; proton p T ~ 1.0 GeV/c STAR Detectors
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DNP 2009, Oct. 13-17, Hawaii6 6 Reconstructed by decay topology Daughter hadrons are identified by dE/dx in TPC Signal to background ratio ~ 1 – 20 (depends on colliding system, particle type and p T ) Particle Identification STAR: preliminary
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DNP 2009, Oct. 13-17, Hawaii7 Participant Plane RP: the reaction plane Defined by the impact parameter Initial geometry: ε std PP: the participant plane Defined by the major axis of the created system Initial geometry: ε part v 2 from the event plane method is sensitive to the participant plane PHOBOS : NPA774: 523 (2006), PRC77, 014906 (2008) S. A. Voloshin, A. M. Poskanzer, A.Tang and G.Wang, PLB, 659 (2008), 537-541
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DNP 2009, Oct. 13-17, Hawaii8 Ideal Hydro Test Ideal hydro fails to reproduce centrality dependence of the data. Fluctuation of v 2 ? Viscosity? Incomplete thermalization? Ideal hydro: P. Huovinen, private communication
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DNP 2009, Oct. 13-17, Hawaii9 System and Energy Dependence Au+Au and Cu+Cu Minimum bias events 200 and 62.4 GeV Event plane Au+Au: TPC Systematic: FTPC, 5% Cu+Cu: FTPC Systematic: v 2 {AA-pp}, 5% NQ scaling De-confinement at RHIC Partonic collectivity Scaled by eccentricity Remove the initial geometry Stronger collective flow in larger system STAR: preliminary STAR Au + Au 62.4 GeV : PRC75, 054906 (2007) ε part {2}: J. Y. Ollitrault, A. M. Poskanzer and S. A. Voloshin, PRC80, 014904 (2009)
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DNP 2009, Oct. 13-17, Hawaii10 Centrality Dependence Au+Au and Cu+Cu at 200 GeV NQ scaling for each centrality bin => partonic collectivity Collectivity: Driven by number of participants, NOT by eccentricity. Larger v 2 / part indicates stronger flow in more central collisions. Hint: the system created in collisions at RHIC is not fully thermalized. STAR: preliminary STAR Au + Au 200 GeV : PRC77, 054901 (2008) S. Voloshin, A. Poskanzer, PL B474, 27(00). D. Teaney, et. al., nucl-th/0110037
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DNP 2009, Oct. 13-17, Hawaii11 Low p T (≤ 2 GeV/c): hydrodynamic mass ordering High p T (> 2 GeV/c): number of quarks ordering s-quark hadron: smaller interaction strength in hadronic medium light- and s-quark hadrons: similar v 2 pattern => Collectivity developed at partonic stage! Partonic Collectivity PHENIX π and p : nucl-ex/0604011v1
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DNP 2009, Oct. 13-17, Hawaii12 The v 2 of the multi-strange hadrons ϕ, Ω Partonic collectivity at RHIC! The observed NQ scaling De-confinement at RHIC! Test thermalization at RHIC Heavy flavor measurements Thermalization at RHIC? Summary
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DNP 2009, Oct. 13-17, Hawaii13 Backup
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DNP 2009, Oct. 13-17, Hawaii14 Assume Borghini et al. Phys. Rev. C70 (2006)4905 KS0KS0 v 2 versus M inv method
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DNP 2009, Oct. 13-17, Hawaii15 Centrality Dependence STAR: preliminary STAR Au + Au 200 GeV : PRC77, 054901 (2008)
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DNP 2009, Oct. 13-17, Hawaii16 Ideal Hydro Test Ideal hydro: P. Huovinen, private communication Ideal hydro fails to reproduce centrality dependence of the data. Fluctuation of v 2 ? Viscosity? Incomplete thermalization? Au+Au at 200 GeV STAR Au + Au 200 GeV : PRC77, 054901 (2008)
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