PHENIX measurements of reaction plane dependence of high-pT photons and pions

Abstract

Direct photon and neutral pion production with respect to the reaction plane at high-pT were measured with the PHENIX experiment in Au+Au collisions at at mid-rapidity. The azimuthal asymmetry parameter v2 for direct photons was found to be consistent with zero for all centrality classes. We evaluate the dependence of π0 suppression at high-pT on the emission angle Δϕ with respect to the event reaction plane for seven centrality bins. For the peripheral bins we observe no suppression for neutral pions aligned with the reaction plane while π0's produced perpendicular to the reaction plane are suppressed by factor 2. We found that a simple geometric picture can explain the observed suppression pattern.