Partonic Collectivity at RHIC
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Transcript of Partonic Collectivity at RHIC
Partonic Collectivity at RHIC
ShuSu Shi
for the STAR collaboration
Lawrence Berkeley National LaboratoryCentral China Normal University
DNP 2009, Oct. 13-17, Hawaii 2
Introduction
STAR Detectors
v2 Results and Discussions System size and Energy Dependence Multi-strange Hadron and Ω
Summary
Outline
DNP 2009, Oct. 13-17, Hawaii 3
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
DNP 2009, Oct. 13-17, Hawaii 4
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
DNP 2009, Oct. 13-17, Hawaii 5
TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.0 GeV/c
STAR Detectors
DNP 2009, Oct. 13-17, Hawaii 66
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
DNP 2009, Oct. 13-17, Hawaii 7
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
DNP 2009, Oct. 13-17, Hawaii 8
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
DNP 2009, Oct. 13-17, Hawaii 9
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)
DNP 2009, Oct. 13-17, Hawaii 10
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
DNP 2009, Oct. 13-17, Hawaii 11
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
DNP 2009, Oct. 13-17, Hawaii 12
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
DNP 2009, Oct. 13-17, Hawaii 15
Centrality Dependence
STAR: preliminary
STAR Au + Au 200 GeV : PRC77, 054901 (2008)
DNP 2009, Oct. 13-17, Hawaii 16
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)