Collective Flow in Heavy-Ion Collisions Kirill Filimonov (LBNL)
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Transcript of Collective Flow in Heavy-Ion Collisions Kirill Filimonov (LBNL)
![Page 1: Collective Flow in Heavy-Ion Collisions Kirill Filimonov (LBNL)](https://reader035.fdocuments.in/reader035/viewer/2022070409/56649e985503460f94b9b619/html5/thumbnails/1.jpg)
Collective Flow in Heavy-Ion Collisions
Kirill Filimonov (LBNL)
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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
• axially symmetric radial flow• azimuthally anisotropic transverse flow
Types of Flow:
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Collective Behavior in non-central Heavy Ion Collisions
b – impact parameter
Low energy heavy-ion collisions: E/A=25 MeV
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Collective Behavior in non-central Heavy Ion Collisions
Relativistic heavy-ion collisions: E/A~0.4-10 GeV
b – impact parameter
“spectators”
“spectators”
“participants”
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Collective Behavior in non-central Heavy Ion Collisions
Passage time: 2R/(βcmγcm)
“spectators”
“spectators”
“participants”
REACTION PLANE
• 15 fm/c at 1 GeV/nucleon• 5.4 fm/c at 10 GeV/nucleon• 1.4 fm/c at 160 GeV/nucleon
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View in transverse plane
TARGET PROJECTILE
Spectator blocking
x
y
Azimuthal anisotropy in momentum space (directed flow)
px
py
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Directed (sideward) FlowExample: E877 (AGS, 11 AGeV)
<px> ≠0
px
py protons deuterons
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Out-of-plane squeeze-out (spectator blocking)
x
y
Azimuthal anisotropy in momentum space (elliptic flow)
px
py
dN/d
-/2 0 /2
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In-plane elliptic flow (due to pressure gradient)
x
y
Azimuthal anisotropy in momentum space (elliptic flow)
px
py
dN/d
-/2 0 /2
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Interplay of passage/expansion times
Passage time: 2R/(βcmγcm)Expansion time: R/cs cs=c√dp/dε - speed of sound
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Sensitivity to nuclear EOSScience, 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:
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Elliptic flow at RHIC
b – impact parameter
“spectators”
“spectators”
Longitudinal and transverse expansion => no influence of spectator matter at midrapidity
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Elliptic flow at RHIC
Reactionplane
In-planeOu
t-o
f-p
lan
e
Y
X
Re-interactions FLOW Re-interactions among what? Hadrons, partons or both?
In other words, what equation of state?
Flow
Flow
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Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b ≈ 4 fm
“central” collisions
b ≈ 6.5 fm
midcentral collisions
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Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b ≈ 4 fmb ≈ 6.5 fmb ≈ 10 fm
peripheral collisions
“v2”
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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
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v2 vs Energy Density
Steady increase with energy density
Close to hydrodynamic limit for most central collisions at RHIC
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Elliptic flow => sensitivity to early system
“Elliptic flow”
• evidence ofcollective motion
• sensitive to early pressure
• evidence for• early thermalization
• QGP in early stage
Hydrodynamiccalculation ofsystem evolution
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Quark-number scaling
At intermediate pT v2 appears to depend on quark-number
For pT/n > 0.6 GeV/c, v2 scales with the number of quarks n, as predicted for hadron formation by quark coalescence
v2hadron (pT
hadron ) nv2quark (pT
quark )
pThadron npT
quark
Pions deviate: perhaps because they are goldstone bosons but also because of resonance decay contributions.
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Conclusions and Outlook
• Elliptic flow at RHIC => Evidence for early pressure
• First time hydro works in heavy ion collisions!
• Indications of re-interaction between constituent quarks
• Will charm flow at RHIC?