"Scaling properties of azimuthal anisotropy of mesons and baryons at RHIC

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"Scaling properties of azimuthal anisotropy of
mesons and baryons at RHIC

• Arkadij Taranenko
• Nuclear Chemistry, SUNY, Stony Brook
• for the PHENIX Collaboration

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Outline

• Motivation
• Fine structure of V2 for mesons and baryons
• Hydro V2 scaling at RHIC
• Scaling tests with the data
• Saturation of elliptic flow at RHIC
• Conclusions

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Why Elliptic Flow ?
Significant Energy Density is produced in AuAu
collisions at RHIC
Thermalization
PRL87, 052301 (2001)
eccentricity
time to thermalize the system (t0 0.2 - 1 fm/c)
eBjorken 5 - 15 GeV/fm3
Elliptic flow is an important probe for high
energy density matter
e drives pressure gradients which result in flow.
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Elliptic Flow _at_ RHIC
(STAR - PRL 92 (2004) 052302 (PHENIX) - PRL 91
(2003) 182301
Reasonable agreement with hydro calculations Is
flow at RHIC Hydrodynamic ? (coalescence, etc ?)
Scaling investigations is crucial for this
question
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Methods of Analysis
TOF timing resolution 120 ps
Analysis performed with the PHENIX detector
PHENIX EMC (PbSc)
New PID results for

• PID analysis is an extension
• of PRL. 91, 182301, 2003 (TOF)
• Differences
• PID analysis with EMCAL (PbSc)
• (6 sectors) TOF detector
• High statistics
• detailed centrality and pT results

EMC timing resolution 400 ps
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v2 sheet for mesons
PHENIX Preliminary
No significant change in shape for meson v2
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v2 sheet for baryons
PHENIX Preliminary
Note shape evolution for baryons
Due to Radial flow ?
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What is the information contained in scaling ?
Scaling Tests
Eccentricity scaling
H. Heiselberg, A. Levy , Phys. Rev C 59 (1999)
2716
Phys. Rev. Lett. 89, 212301 (2002), 
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Scaling of azimuthal anisotropy for charged
hadrons
PHENIX Preliminary
PHENIX Preliminary
PHENIX Preliminary

• The differential anisotropy scales with the
  integral anisotropy-integral flow is monotonic
  and linearly related to the eccentricity over a
  broad range of centralities
• Scale invariant variable
• The scaling property is also indicative of a
  factorization of
• v2 (b,pT) v2(b) v2(pT)

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Scaling of azimuthal anisotropy for identified
particles
PHENIX Preliminary
PHENIX Preliminary

• v2(pT) for mesons show similar pattern for all
  centralities
• Scaling works over a broad range of centralities

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Scaling properties of azimuthal anisotropy of
baryons
PHENIX Preliminary
PHENIX Preliminary

• Scaling is less robust for baryons
• This is due to shape changes of v2(pT) with
  centrality

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Scaling test for baryons (II)
PHENIX Preliminary
PHENIX Preliminary
scaling more robust via centrality grouping
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Fine Structure Scaling
M. Csanad et al, Nucl Phys A 742 (2004) 80-94
- for different particle species should scale !!
- mass dependent scale factor
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Scaling Test with Hydro
P. Huovinen, P.F. Kolb .. Phys. Lett. B50358
(2001)
Straight forward scaling observed
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Scaling PHENIX Data
PHENIX Preliminary
5ltCentralitylt30

• apparent scaling
• scaling breaks early for kaons

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Scaling of RHIC data

• Demonstration of Comprehensive scaling at RHIC

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Higher harmonic scaling at RHIC
STAR data nucl-ex/0409033
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Elliptic flow - Excitation function

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Elliptic Flow Excitation Function
Results are strikingly similar for
V2 decreases by 50 from RHIC to SPS
PHENIX - nucl-ex/0411040
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Excitation function for differential v2
Apparent saturation of v2 for
Possible indication for a soft EOS ! Signal for
a Mixed phase ?
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Conclusions

• Large array of detailed v2 measurements can be
  summarized via scaling rules
• The fine structure of v2 at RHIC is compatible
  with hydrodynamic flow

• Early thermalization
• Strongly interacting matter

Excitation function indicate saturation of v2 At
RHIC possible indication of mixed phase?
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Elliptic Flow_at_ AGS
Low Energy Squeeze-out
High Energy In-plane
Pressure Gradients Drive Transverse and Elliptic
flow
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(E895) - PRC 66 (2001), 021901

• The Essentially Linear Dependence of Squeeze-out
  is Very Well Understood

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Elliptic Flow_at_ SIS/AGS
(KAOS Z. Phys. A355 (1996) (E895) - PRL 83
(1999) 1295
Scaling by the passing time is observed
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