The Study of Azimuthal Distribution for High pT Charged Hadron at RHIC-PHENIX

1. The Study of Azimuthal Distribution for High pT Charged Hadron at RHIC-PHENIX Maya SHIMOMURA for the PHENIX Collaboration University of Tsukuba

2. non central collision z φ Ｙ Beam axis Reaction plane Ｙ x x (Reaction Plane) About Elliptic Flow (v2) v2 indecates the strength of the azimuthal anisotropy for the produced particles. Important probe to study property of the dense matter made by heavy ion collisions Fourier expanding of the distribution of produced particle angle, Φ, to RP v2is the coefficient of the second term -> indicates ellipticity If yield is (x direction)>(y direction), v2 >0. We detect Initial geometrical anisotropy transferring the anisotropy in momentum space.  measurand reflected by the dense matter produced by collisions

3. PRL 94, 232302 Motivation From Know results v2 at Low pT (< 2.0~3.0 GeV/c) can be explaned by hydro-dynamics and initial pressure gradient At higher pT, particles produced from jet-fragmentation made by initial collisions.  Non zero v2, because jets lose its energy related to the path length in the medium and the medium has geometrical anisotropy due to the participant shape. Large energy loss Small energy loss Can v2 be scaled by the ellipticity of the participants from low pT to higher pT, even though the mechanisms are different? v2(pT)of 62.4GeV, 200GeV（AuAu） and 130GeV(PbPb) are consistent. v2 decrease to ~50% at 17.2GeV(PbPb) v2 looks like saturated at RHIC energy. Can the different results be observed at different system （AuAu,CuCu）or/and different collision energy （200GeV, 62.4GeV)?

4. <PHENIX detectors> DC + PC1for good track selection and to determine p EMCALfor Energy cut PC2+PC3for track confirmation BBC to determine reaction plane and vertex Analysis <The data for this analysis> • Au+Au and Cu+Cu collision • Taken in 2003-2005 at RHIC-PHENIX • Collision Energy: 62.4 and 200GeV/nucleon <Reaction Plane determine> Reaction Plane is determined by measuring the azimuthal distribution of produced particles by north and south Beam-Beam Counter placed at || ~ 3 – 4. <Background rejection> The particles such as decayed ,which miss-reconstructed as the high momentum particles are BG. Energy/momentum > 0.2 Cut rejects that kind of BG.

5. Au Au 62.4 and 200GeV comparison (1) The results of 62.4GeV and 200GeV have good agreement at each centralities.

6. 2.0-4.0 GeV/c 1.0-2.0 GeV/c 0.2-1.0 GeV/c Au Au 62.4 and 200GeV comparison (2) ellipticity of participant Black 200GeV Red 62.4GeV v2/eccentricity vs. Npart has different slope for different pT Almost constant at low ｐT→v2 can be scaled by eccentricity 62.4GeV and 200GeV have good agreement.  consistent to past results

7. Cu Cu 62.4 and 200GeV comparison (1) The results of 200 and 62.4GeV are consistent within errors.

8. Cu Cu 62.4 and 200GeV comparison (2) Black 200GeV Red 62.4GeV 1.0-2.0 GeV/c 0.2-1.0 GeV/c Look like there are some difference between the results of 200 and 62.4GeV compared with AuAu results. (but consistent within errors). v2/eccentricity is linear to Npart except most central collisions （Eccentricity is small and its error is large at central collisions. ）

9. 1.0-2.0 GeV/c 0.2-1.0 GeV/c Comparison of 62.4 and 200GeV at AuAu and CuCu (1) v2 is not scaled by Npart. Black AuAu 200GeV Red AuAu 62.4GeV Green CuCu 200GeV Blue CuCu 62.4GeV

10. 2.0-4.0 GeV/c 1.0-2.0 GeV/c 0.2-1.0 GeV/c Comparison of 62.4 and 200GeV at AuAu and CuCu (2) Black AuAu 200GeV Red AuAu 62.4GeV Green CuCu 200GeV Blue CuCu 62.4GeV v2 is scaled by eccentricity. （There are different eccentricity calculation especially for central collision which is not on the lines.→Back up） The results of CuCu 62.4GeV are not scaled with the same slope of others. → There are system dependence. v2 scaled by eccentricity is saturated when the energy density of produced matter is enough high.

11. Summary • Obtained v2 analyzing AuAu 200, AuAu 62.4, CuCu 62.4GeV, (CuCu200GeV) taken at RHIC-PHENIX in 2003-2005. • AuAu 62.4 v2(pT) and 200GeV v2(pT) have good agree. • CuCu 62.4 v2(pT) and 200GeV v2(pT) agree within errors. • v2 is not scaled by Npart and is scaled by eccentricity. The slopes are different for different system and pT →CuCu 62.4 GeV looks different from others. （still systematic erros are too big to state it.） • When the energy density of dense matter is enough high, the eccentricity can scale v2 with certain slope ??? →need more detail study.

12. 13 Countries; 62 Institutions; 550 Participants* *as of March 2005

13. Perfect Liquid (brand name) found the QGP in bathroom ?

14. Back up Including another comparisons

15. <analysis method> • PC3 sdphi distribution at different pT region • Yield vs pT at different e/p cut 1 2 PC3 [dphi/σ] E/p>0.2 cut

16. 2.5σ integration The ratio of signal to BG w/wo E/p cut Ref  Ana note 473 E/p >0.2 signal no E/p cut E/p > 0.2 cut seems to be reasonable to remove BG. BG

17. Reaction plane resolution • BBC North + South combined • √(2*<cos(2*(ΨS –ΨN))>) =1/correction factor

18. Another eccentricity calculation Phobos at QM05

19. 2.0-4.0 GeV/c 1.0-2.0 GeV/c 0.2-1.0 GeV/c Cu Cu 62.4 and 200GeV comparison (2) Black 200GeV Red 62.4GeV Look like there are some difference between the results of 200 and 62.4GeV compared with AuAu results. (but consistent within errors). v2/eccentricity is linear to Npart except most central collisions （Eccentricity is small and its error is large at central collisions. ）

20. Comparison of 62.4 and 200GeV at AuAu and CuCu Black AuAu 200GeV Red AuAu 62.4GeV Green CuCu 200GeV Blue CuCu 62.4GeV 2.0-4.0 GeV/c 1.0-2.0 GeV/c 0.2-1.0 GeV/c

21. Comparison of 62.4 and 200GeV at AuAu and CuCu CuCu 62.4 results are not scaled as others. 黒・赤： AuAu 緑・青： CuCu There are more than one definition for eccentricity, and results at large (and small) eccentricity could change.