Partonic Collectivity at RHIC

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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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Partonic Collectivity at RHIC. ShuSu Shi for the STAR collaboration Lawrence Berkeley National Laboratory Central China Normal University. Outline. Introduction STAR Detectors v 2 Results and Discussions System size and Energy Dependence Multi-strange Hadron  and Ω - PowerPoint PPT Presentation

Transcript of Partonic Collectivity at RHIC

Page 1: Partonic Collectivity at RHIC

Partonic Collectivity at RHIC

ShuSu Shi

for the STAR collaboration

Lawrence Berkeley National LaboratoryCentral China Normal University

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Introduction

STAR Detectors

v2 Results and Discussions System size and Energy Dependence Multi-strange Hadron and Ω

Summary

Outline

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T < T conf

T > T conf

constant potential

linea

r pot

entia

l

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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2 2

2 2

y x

y x

12 cos 2 , tan ( )y

x

pv

p

Elliptic Flow (v2)

Coordinate-SpaceAnisotropy

Momentum-SpaceAnisotropy

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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TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.0 GeV/c

STAR Detectors

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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 pT)

Particle Identification

STAR: preliminary

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Participant Plane

RP: the reaction plane Defined by the impact parameterInitial geometry: εstd

PP: the participant plane Defined by the major axis of the created system Initial geometry: εpart

v2 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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Ideal Hydro Test

Ideal hydro fails to reproduce centrality dependence of the data.

Fluctuation of v2? Viscosity? Incomplete thermalization?

Ideal hydro: P. Huovinen, private communication

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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: v2{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)εpart{2}: J. Y. Ollitrault, A. M. Poskanzer and S. A. Voloshin,PRC80, 014904 (2009)

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Centrality Dependence

Au+Au and Cu+Cu at 200 GeVNQ scaling for each centrality bin => partonic collectivityCollectivity: Driven by number of participants, NOT by eccentricity.

Larger v2/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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Low pT (≤ 2 GeV/c): hydrodynamic mass orderingHigh pT (> 2 GeV/c): number of quarks ordering

s-quark hadron: smaller interaction strength in hadronic medium light- and s-quark hadrons: similar v2 pattern

=> Collectivity developed at partonic stage!

Partonic Collectivity

PHENIX π and p: nucl-ex/0604011v1

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The v2 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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Backup

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2

2 2

( ) cos(2( )

( ) ( ) ( )

Sig Bginv r

Sig Bginv inv inv

v m

Sig Bgv m v m m

Sig Bg Sig Bg

2 ( ) ( )Bginv invv m f mAssume

Borghini et al. Phys. Rev. C70 (2006)4905

KS0

v2 versus Minv method

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Centrality Dependence

STAR: preliminary

STAR Au + Au 200 GeV : PRC77, 054901 (2008)

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Ideal Hydro Test Ideal hydro: P. Huovinen, private communication

Ideal hydro fails to reproduce centrality dependence of the data.

Fluctuation of v2? Viscosity? Incomplete thermalization?

Au+Au at 200 GeV

STAR Au + Au 200 GeV : PRC77, 054901 (2008)