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Collective Flow in Heavy-Ion Collisions

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What is Flow in Heavy-Ion Collisions? ... Azimuthal anisotropy in momentum space (directed flow) px. py. Directed (sideward) Flow ... – PowerPoint PPT presentation

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Title: Collective Flow in Heavy-Ion Collisions


1
Collective Flow in Heavy-Ion Collisions
  • Kirill Filimonov (LBNL)

2
What is Flow in Heavy-Ion Collisions?
  • Collective motion characterized by space-momentum
    correlation of dynamic origin
  • Concept from Hydrodynamics
  • - hot and compressed matter
    behaves like a compressible fluid

Types of Flow
  • axially symmetric radial flow
  • azimuthally anisotropic transverse flow

3
Collective Behavior in non-central Heavy Ion
Collisions
Low energy heavy-ion collisions E/A25 MeV
4
Collective Behavior in non-central Heavy Ion
Collisions
Relativistic heavy-ion collisions E/A0.4-10 GeV
5
Collective Behavior in non-central Heavy Ion
Collisions
Passage time 2R/(ßcm?cm)
  • 15 fm/c at 1 GeV/nucleon
  • 5.4 fm/c at 10 GeV/nucleon
  • 1.4 fm/c at 160 GeV/nucleon

6
View in transverse plane
7
Directed (sideward) Flow
Example E877 (AGS, 11 AGeV)
py
protons deuterons
px
ltpxgt ?0
8
Out-of-plane squeeze-out (spectator blocking)
Azimuthal anisotropy in momentum space
(elliptic flow)
9
In-plane elliptic flow (due to pressure gradient)
Azimuthal anisotropy in momentum space
(elliptic flow)
10
Interplay of passage/expansion times
Passage time 2R/(ßcm?cm) Expansion time R/cs
cscvdp/de - speed of sound
11
Sensitivity to nuclear EOS
Science, Vol 298, Issue 5598, 1592-1596, 22
November 2002Determination of the Equation of
State of Dense Matter Pawel Danielewicz, Roy
Lacey, William G. Lynch
Directed Flow
Elliptic flow
12
Elliptic flow at RHIC
Longitudinal and transverse expansion gt no
influence of spectator matter at midrapidity
13
Elliptic flow at RHIC
Flow
Y
Out-of-plane
In-plane
Reaction plane
Flow
X
Re-interactions ? FLOW Re-interactions among
what? Hadrons, partons or both? In other words,
what equation of state?
14
Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b 6.5 fm
b 4 fm
central collisions
midcentral collisions
15
Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b 10 fm
b 6.5 fm
b 4 fm
peripheral collisions
16
v2 Excitation Function
Rich structure Transition from in-plane to
out-of-plane and back to in-plane
emission Geometry effect in addition to
(smooth?) change in pressure
17
v2 vs Energy Density
Steady increase with energy density Close to
hydrodynamic limit for most central collisions at
RHIC
18
Elliptic flow gt sensitivity to early system
  • Elliptic flow
  • evidence ofcollective motion
  • sensitive to early pressure
  • evidence for
  • early thermalization
  • QGP in early stage

Hydrodynamic calculation of system evolution
19
Quark-number scaling
At intermediate pT v2 appears to depend on
quark-number For pT/n gt 0.6 GeV/c, v2 scales with
the number of quarks n, as predicted for hadron
formation by quark coalescence
Pions deviate perhaps because they are goldstone
bosons but also because of resonance decay
contributions.
20
Conclusions and Outlook
  • Elliptic flow at RHIC gt Evidence for early
    pressure
  • First time hydro works in heavy ion collisions!
  • Indications of re-interaction between constituent
    quarks
  • Will charm flow at RHIC?
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