in

p  0

s v

2 NN

analysis = 200GeV Au+Au collisions

KANETA, Masashi

for the PHENIX Collaboration RIKEN-BNL Research Center

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 1

Why Event Anisotropy?

• Because of sensitive to collision geometry – In low p T (~<2 GeV/c) • Pressure gradient of early stage • Hydrodynamical picture is established – In high p T (>~2 GeV/c) • Energy loss in dense medium (Jet Quenching) • Partonic flow(?) Here we focus on ellipticity of azimuthal momentum distribution, v 2 (second Fourier coefficient) z y Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) x 2

Method of

p 0

v

2

Measurement

• Define reaction plane by charged multiplicity on Beam-Beam Counters • p 0 reconstruction from gamma measured by Electro-Magnetic Calorimeter (EMC) • For each p T , azimuthal angle, centrality • Combine both information – Counting number of p 0 as a function of

E dN

3

d

3

p

 1 2 p

d

2

N p T dp T dy

  1 

n

   1 2

v n measured

cos[

n

   

r

 ]   where

n

 1 , 2 , 3 ,....

event anisotropy parameter measured azimuthal angle of the particle reaction plane angle v n real = v n measured / ( reaction plane resolution ) n Note: the detail of reaction plane definition will be found in

nucl-ex/0305013

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 3

PHENIX experiment

• Lead Scintillator and Lead Glass EMCs – Gamma measurement ( p 0 gg ) • BBCs and ZDCs – Collision centrality determination • BBCs – Reaction plane determination and – Its resolution correction Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 4

Example plots from the analysis procedure

Invariant mass of gg from same event and mixed event (classed by reaction plane, centrality, vertex position) 200GeV Au+Au normalization range for combinatorial B.G.

subtraction After subtraction, there is 2nd component of B.G. in p T <2GeV/c region shape assumed as linear+asym. Gauss m gg [GeV/c 2 ] m gg [GeV/c 2 ] count number of p 0 in a range after 2nd B.G. subtraction (not used the fit function) F R [rad] Fit function: (average of p 0 count)  ( 1 + 2 v 2 Green lines : deviation by error of v 2 cos[2(  F R )]) Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 5

Tooooooooooooo many histograms checked

Example of invariant mass distributions for each p T ,  F R in a centrality bin Before combinatorial background subtraction After combinatorial background subtraction p 0 as a function of F Rb Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 6

v

2

vs. p

T

vs. Centrality from 200GeV Au+Au

Systematic error from p 0 Statistical error is shown by error bar count method and reaction plane determination is shown by gray box phenix preliminary Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 7

v

2

vs. p

T

vs. Centrality from 200GeV Au+Au

Systematic error from p 0 Statistical error is shown by error bar count method and reaction plane determination is shown by gray box The charged p and

K

v 2 are shown only with statistical errors phenix preliminary } nucl-ex/0305013 • Charged p + K v 2 consistent with p 0 v 2 in p T <4GeV/c Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 8

v

2

vs. p

T

(Minimum Bias) from 200GeV Au+Au

• Identified particle v 2 up to p T =10GeV/c phenix preliminary 36.3

 10 6 [events] = 5.3

+0.5-0.4

[( m b) -1 ] Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 9

v

2

vs. p

T

(Minimum Bias) from 200GeV Au+Au

• Identified particle v 2 up to p T =10GeV/c phenix preliminary } nucl-ex/0305013 36.3

 10 6 [events] = 5.3

+0.5-0.4

[( m b) -1 ] Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 10

v

2

vs. p

T

(Minimum Bias) from 200GeV Au+Au

• Identified particle v 2 up to p T =10GeV/c phenix preliminary nucl-ex/0305013 36.3

 10 6 [events] = 5.3

+0.5-0.4

[( m b) -1 ] Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 11

Comparison with K

0 S

and

L

(STAR)

STAR data from nucl-ex/0306008 Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 12

Comparison with a model

phenix preliminary Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 13

Comparison with a model

phenix preliminary Special thanks to C. Nonaka (one of authors) of nucl-th/0306027 for data of model calculation Comparison with a model which is described in nucl-th/0306027. Here we don't want to discuss which model can describe the data. To conclude which model can describe the data, we need much more statistics in high p T region.

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 14

Summary

• First measurement of p 0 – In

p T

=1-10 GeV/c • Charged p + K v 2 – In

p T

=1-4GeV/c v 2 at RHIC consistent with p 0 v 2 • Minimum bias data shows finite p 0 v 2 – Up to

p T

~8 GeV/c • RHIC run4 Au+Au, it will be – Much more statistics • Detail study of v 2 shape around p

T

=2-4GeV/c – Much higher p

T

• We want to know where is end of finite v 2 in very high p

T

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 15