Collective Flow

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Collective Flow

• Art Poskanzer

Exploring the secrets of the universe
Color by Roberta Weir
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Photos
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Spectator-Participant Picture
1973
Abrasion and Ablation of Heavy Ions, J.D. Bowman,
W.J. Swiatecki, and C.F. Tsang, LBL-2908 (1973)
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Fireball
G.D. Westfall et al., Phys. Rev. Letters 37, 1202
(1976)
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Centrality Dependence
Peripheral Collision
(near) Central Collision
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Transverse Plane
H. Wieman (2005)
around the beam axis
S p x y
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Elliptic Flow
Animation by Jeffery Mitchell (Brookhaven
National Laboratory)
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Nuclear Collisions
1975
Explored to date only on the axes.
W.J. Swiatecki, Bevalac Upgrade Proposal, 1975.
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Kinds of Flow
mainly spectator matter
self quenching early time
temperature
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Plateau
1984
Temperature or Pressure
direct photons elliptic flow
Beam Energy
W. Swiatecki (1984)
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v2 /?
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Azimuthal Flow Angle
S. Voloshin and Y. Zhang, Z. Phys. C 70, 665
(1996)
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Fourier Harmonics
Event plane resolution correction made for each
harmonic
Unfiltered theory can be compared to experiment!
S. Voloshin and Y. Zhang, hep-ph/940782 Z. Phys.
C 70, 665 (1996)
See also, J.-Y. Ollitrault, arXiv nucl-ex/9711003
(1997)
and J.-Y. Ollitrault, Nucl. Phys. A590, 561c
(1995)
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Methods of Analysis

• Pair-wise
• Standard
• Scalar Product
• q-dist
• Cumulant
• Lee-Yang Zeros

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Directed and Elliptic Flow at the SPS
NA49, C. Alt et al., PRC 68, 034903 (2003)
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STAR
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First RHIC Elliptic Flow
First paper from STAR
130 GeV/A AuAu
22 k events
Data approach hydro for central collisions
STAR, K.H. Ackermann et al., PRL 86, 402 (2001)
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Elliptic Flow vs. Beam Energy
25 most central mid-rapidity
all v2
bounce-off
In-plane elliptic flow
squeeze-out
six decades
A. Wetzler (2005)
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Directed Flow from Mixed Harmonics
Removes nonflow Uses best determined event plane
STAR, J. Adams et al., PRC submitted (2005)
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v1 from Spectator Neutrons
Zero-Degree Calorimeter Shower Max Detector
for transverse deflection of spectator neutrons
A. Tang, STAR
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Quark Coalescence
D. Molnar and S.A. Voloshin, Phys. Rev. Letters
91, 092301 (2003) STAR, Phys. Rev. C 72, 014904
(2005)
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Higher Harmonics
vn 1.2 v2n/2
more details of the event shape in p space quarks
have v4
J. Adams et al., PRL 92, 062301 (2004)
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Conclusions from Flow

• Hydrodynamics at top RHIC Energy
• Thermalization
• Parton Coalescence
• Partonic Phase
• Thermalized Partonic Phase
• Quark-Gluon Plasma