KANETA, Masashi

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p0 v2 analysisin ?sNN 200GeV AuAu collisions

• KANETA, Masashi
• for the PHENIX Collaboration
• RIKEN-BNL Research Center

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Why Event Anisotropy?

• Because of sensitive to collision geometry
• In low pT (lt2 GeV/c)
• Pressure gradient of early stage
• Hydrodynamical picture is established
• In high pT (gt2 GeV/c)
• Energy loss in dense medium (Jet Quenching)
• Partonic flow(?)

Here we focus on ellipticity of
azimuthal momentum distribution, v2 (second
Fourier coefficient)
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Method of p0 v2 Measurement

• Define reaction plane by charged multiplicity on
  Beam-Beam Counters
• p0 reconstruction from gamma measured by
  Electro-Magnetic Calorimeter (EMC)
• For each pT, azimuthal angle, centrality
• Combine both information
• Counting number of p0 as a function of

event anisotropy parameter measured
reaction plane angle
azimuthal angle of the particle
vnreal vnmeasured/ (reaction plane resolution)n
Note the detail of reaction plane definition
will be found in nucl-ex/0305013
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PHENIX experiment

• Lead Scintillator and Lead Glass EMCs
• Gamma measurement (p0?gg)
• BBCs and ZDCs
• Collision centrality determination
• BBCs
• Reaction plane determination and
• Its resolution correction

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Example plots from the analysis procedure
Invariant mass of gg from same event and mixed
event (classed by reaction plane, centrality,
vertex position)
After subtraction, there is 2nd component of B.G.
in pTlt2GeV/c region
200GeV AuAu
normalization range for combinatorial
B.G. subtraction
shape assumed as linearasym. Gauss
mgg GeV/c2
mgg GeV/c2
count number of p0 in a range after 2nd B.G.
subtraction (not used the fit function)
Fit function (average of p0 count) ? ( 1 2 v2
cos2(f - FR)) Green lines deviation by error
of v2
f-FR rad
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Tooooooooooooo many histograms checked
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v2 vs. pT vs. Centrality from 200GeV AuAu
Statistical error is shown by error
bar Systematic error from p0 count method and
reaction plane determination is shown by gray box
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v2 vs. pT vs. Centrality from 200GeV AuAu
Statistical error is shown by error
bar Systematic error from p0 count method and
reaction plane determination is shown by gray box
The charged p and K v2 are shown only with
statistical errors

• Charged pK v2 consistent with p0 v2 in pTlt4GeV/c

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v2 vs. pT (Minimum Bias) from 200GeV AuAu

• Identified particle v2 up to pT10GeV/c

36.3?106 events 5.30.5-0.4 (mb)-1
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v2 vs. pT (Minimum Bias) from 200GeV AuAu

• Identified particle v2 up to pT10GeV/c

36.3?106 events 5.30.5-0.4 (mb)-1
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v2 vs. pT (Minimum Bias) from 200GeV AuAu

• Identified particle v2 up to pT10GeV/c

36.3?106 events 5.30.5-0.4 (mb)-1
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Comparison with K0S and L (STAR)
STAR data from nucl-ex/0306008
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Comparison with a model
phenix preliminary
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Comparison with a model
phenix preliminary
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Summary

• First measurement of p0 v2 at RHIC
• In pT1-10 GeV/c
• Charged pK v2 consistent with p0 v2
• In pT1-4GeV/c
• Minimum bias data shows finite p0 v2
• Up to pT8 GeV/c
• RHIC run4 AuAu, it will be
• Much more statistics
• Detail study of v2 shape around pT2-4GeV/c
• Much higher pT
• We want to know where is end of finite v2 in very
  high pT

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Reaction plane resolution
This values are used to correct measured v2