Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 1 KANETA, Masashi for the PHENIX Collaboration RIKEN-BNL Research Center  0 v 2 analysis in  s NN = 200GeV Au+Au collisions

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 2 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(?) x z y Here we focus on ellipticity of azimuthal momentum distribution, v 2 (second Fourier coefficient)

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 3 Method of  0 v 2 Measurement Define reaction plane by charged multiplicity on Beam-Beam Counters  0 reconstruction from gamma measured by Electro-Magnetic Calorimeter (EMC) For each p T, azimuthal angle, centrality Combine both information –Counting number of  0 as a function of 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/

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 4 PHENIX experiment Lead Scintillator and Lead Glass EMCs –Gamma measurement ( 0 ) 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) 5 Example plots from the analysis procedure Invariant mass of  from same event and mixed event (classed by reaction plane, centrality, vertex position) 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 count number of  0 in a range after 2nd B.G. subtraction (not used the fit function) m  [GeV/c 2 ]  R [rad] Fit function: (average of  0 count)  ( v 2 cos[2(  -  R )]) Green lines : deviation by error of v 2 200GeV Au+Au m  [GeV/c 2 ]

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

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 Statistical error is shown by error bar Systematic error from  0 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) 8 } nucl-ex/ phenix preliminary v 2 vs. p T vs. Centrality from 200GeV Au+Au Statistical error is shown by error bar Systematic error from  0 count method and reaction plane determination is shown by gray box Charged + K v 2 consistent with  0 v 2 in p T <4GeV/c The charged  and K v 2 are shown only with statistical errors

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 9 phenix preliminary v 2 vs. p T (Minimum Bias) from 200GeV Au+Au Identified particle v 2 up to p T =10GeV/c 36.3  10 6 [events] = [(  b) -1 ]

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 10 } nucl-ex/ phenix preliminary v 2 vs. p T (Minimum Bias) from 200GeV Au+Au Identified particle v 2 up to p T =10GeV/c 36.3  10 6 [events] = [(  b) -1 ]

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 11 phenix preliminary nucl-ex/ v 2 vs. p T (Minimum Bias) from 200GeV Au+Au Identified particle v 2 up to p T =10GeV/c 36.3  10 6 [events] = [(  b) -1 ]

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 12 Comparison with K 0 S and  (STAR) STAR data from nucl-ex/

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

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 14 Comparison with a model which is described in nucl-th/ 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. Special thanks to C. Nonaka (one of authors) of nucl-th/ for data of model calculation Comparison with a model phenix preliminary

Masashi Kaneta, RBRC, BNL 2003 Fall Meeting of the Division of Nuclear Physics (2003/10/31) 15Summary First measurement of  0 v 2 at RHIC –In p T =1-10 GeV/c Charged + K v 2 consistent with  0 v 2 –In p T =1-4GeV/c Minimum bias data shows finite  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) 16 Reaction plane resolution This values are used to correct measured v 2