Flow at RHIC within the BlastWave framework

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Flow at RHIC within the Blast-Wave framework

• Fabrice Retière
• Lawrence Berkeley National Lab

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QGP and ultra-relativistic heavy-ion collisions
QGP?
Hadronisation
Hadron gas
Au-Au collisions
Jet absorption
Hydrodynamic flow
3
Everything is jets?
Central
STAR preliminary
Peripheral
4
Outline

• Hydrodynamic flow
• Blast-Wave parameterization
• Data self-consistency
• A tool to study the system expansion
• A tool to assess partonic collectivity?
• Summary and outlook

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The initial state drives flow
Dash lines Au hard sphere edge
Y
Out-of-plane
In-plane
Reaction plane
X
Analogy with Li Atom trap
Y
X
Time
6
Building up hydrodynamic flow
Time
Hydro from P. Kolb ,U.Heinz, review for 'Quark
Gluon Plasma 3, nucl-th/0305084
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Hydrodynamic and v2
Au-Au at 130 GeV
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Hydrodynamic and spectra
Au-Au at 130 GeV
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Side explanationFlow and HBT
PT160 MeV/c
PT380 MeV/c
Rside
Rside
Rout
Rout
Dt
Time
Rlong
Sketch by Scott Pratt
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Hydrodynamic and HBT
Au-Au at 130 GeV
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Model vs parameterization

• Hydro
• agree with data at best qualitatively
• Describe the evolution of the system
• Provide an equation of state
• has some predictive power

• Blast-Wave parameterization
• Inspired by hydro
• Does not describe the system evolution
• Tunable
• Has to reproduce data quantitatively
• Good for
• Testing the self-consistency of the flow picture
• Characterizing flow

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The blast wave parameterizationA snap-shot of
the system final state

• Hydro-inspired parameterization
• Boost invariant longitudinal flow
• Transverse flow
• Linear rapidity profile
• Azymuthal oscillation in non-central
• Tunable system size, shape and life time

Parameterization of the final state
Spectra fits application described by
E.Schnedermann, J. Sollfrank, and U. Heinz, PRC
48 (2002) 2462
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Fit to PHENIX data in AuAu at 200 GeV
Spectra
T106 1 MeV ltbInPlanegt 0.571 0.004
c ltbOutOfPlanegt 0.540 0.004 c RInPlane 11.1
0.2 fm ROutOfPlane 12.1 0.2 fm Life time
(t) 8.4 0.2 fm/c Emission duration 1.9
0.2 fm/c c2/dof 120 / 86
v2
HBT
Latest paper (long legacy), F.R and
M.Lisa nucl-th/0312024
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Example of self-consistencyThe Blast Wave
parameterization

• Simultaneous fit to
• Spectra
• v2
• HBT radii
• Shift between pion and kaon average emission
  point
• Could such self-consistency be reached in a
  jet-motivated framework?

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Characterizing flow 2 interesting questions
(among others)

• Did the system expand?
• If the dynamics is driven by jets it presumably
  would not
• If it expands what drives the expansion?
• Do all particle flow the same way?
• If not what could cause the difference?

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The initial state

• Glauber calculation

5-10
10-20
20-30
30-50
50-80
0-5
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Spatial expansion as seen by HBT
STAR preliminary
200 GeV collisions Au-Au d-Au p-p
No expansion limit
Glauber calculation
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Measuring the shape of the system at freeze-out

• The system starts with an elliptical shape
• In what shape does it end up?

Rout-of-plane
Rside (small)
Rside (large)
out-of-plane extended source
Reaction plane
Rin-plane
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How do the edge of the system expand

• Rinitial from Glauber
• Ansatz to deal with fuzzy edges Rinitial 2
  RMSinitial
• Rfinal from Blast-Wave
• Fit to azimuthally sensitive HBT

STAR preliminary
Final state
In-plane
Initial state
Expansion by a factor of 2
Nparticipants
Out-of-plane
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Initial energy density gradient drive the
expansion

• Estimator of the pressure gradients
• Energy density scale with N charged particles
• Scale with the distance between the hot center
  and vaccum
• Estimated by the initial source RMS

STAR preliminary
Work done with M. Lopez-Noriega (Ohio SU)
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This scaling does not hold going to lower energy
STAR preliminary
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Do all particle behave the same way?

• Fit spectra and v2 for different particle species
• Fits to spectra
• Temperature. Decrease as system cools down
• Flow velocity. Increases with time.
• Fits to v2
• Flow velocity modulation. Saturates early?
• Spatial eccentricity. Decreases with time.

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X behaves fit parameter are different than p, K,
p at RHIC
Central PbPb at vs 17 GeV
Central AuAu at vs 200 GeV
Minbias AuAu at vs 200 GeV
Miss X Message would be different
asHBT
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The Blast Wave side of the story Early freeze-out
of X and W
p,K,p spectra PHENIX (box) STAR (circle)
__ 1 s contour
0.6

W and X spectra STAR preliminary
0.4
ltbTgt and eccentricity
Glauber 0.3

• v2 (STAR preliminary)

0.2
p asHBT (STAR)
p,K,p v2 (PHENIX)
Initial flow 0
300
200
100
Temperature (MeV)
Initial state
Time
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Summary

• Blast-Wave assess self consistency of the data
  within a flow-motivated framework
• Clear spatial expansion
• Scale with initial density gradient at a given vs
• X do not behave as p, K, p within this framework
• Suggest early freeze-out
• Hint of partonic collectivity
• The Blast-Wave is a powerful tool for
  characterizing flow
• Or subtracting flow if you want to study jet
  effects
• But are they completely independent?
• If you want the code write me an email
  (fgretiere_at_lbl.gov)
• It does not replace a real model though

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Outlook at LHC energyA significant increase of
Rside
At LHC 13-16 fm ? Rside 10 fm in central Pb-Pb
at LHC
200-250
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Back-up
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Blast wave parameterization 2

• Hydro-like parameterization
• Boltzman with Flow
• Flow r(r) (r0 ra cos(2fp)) r
• Grows linearly increasing r
• May vary with angle wrt event plane
• Parameters T, r0 and ra
• System geometry
• Elliptical box (fuzzy edges possible)
• Parameters Rx (in-plane) and Ry (out-of-plane)
• Time
• Parameters proper life time (t) and emission
  duration (Dt)

To calculate - Spectra integral over
space and momentum azimuthal angle - v2(pt)
average of cos(2fp)over space at a given pt -
Hbt radii (pt) standard deviations along out,
side and long directions at A given pt
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Non-flow issues

• v2
• Scalar products(1)
• Sensitive to both flow and non-flow
• Df correlation
• Disentangle jets from flow
• Lee-Yang zeroes(2) and high order cumulants
• Cumulants even from PHENIX(3)

STAR preliminary, vs200 GeV

• A. Tangs talk
• N. Borghinis talk
• M. Issahs poster

p-p is the non-flow baseline
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5-10
10-20
20-30
30-50
50-80
0-5
Au-Au
0-20
20-40
40-100
d-Au