Systematic study of v2 at 62.4 and 200 GeV in Cu + Cu and Au + Au Collisions at RHIC-PHENIX

Abstract

The transverse momentum (PT) and centrality dependence of the azimuthal anisotropy (v2) are measured for charged hadron species at 62.4 and 200 GeV in Cu + Cu and Au + Au collisions by the PHENIX experiment at RHIC. The results are consistent with eccentricity scaling and with quark number (nq) + transverse kinetic energy (KEt) scaling. Also, we found that v2 divided by the participant eccentricity of the initial geometry proportionally increases with the number of participants to the 1/3 power except at small Npart in Cu+Cu at = 62.4 GeV. Taking these scalings (nq, KET, eccentricity and N1/3part) into account, there is a universal scaling for v2 with different energies, collision sizes and particle species. The results indicate that v2 is determined by more than just the geometrical eccentricity and also depends on the size of the collision. Moreover, using blast wave fitting, we report that both the behaviors of v2 and PT distributions can be understood from the thermal nature of produced particles based on hydro-dynamical behavior.