Search for Direct Photons from $\sqrt{s_{NN}}=200GeV$ AuAu Collisions Using a New $\pi^{0}$ Tagging Method in the PHENIX Experiment at RHIC

Abstract

Direct photons provide a insightful tool to study the different stages of a heavy ion collision, especially the formation of a quark-gluon plasma, without being influenced by the strong interaction and hadronization processes. The yield of direct photons can be determined based on the inclusive photon yield and the background from hadronic decays. We present a new analysis technique applied to PHENIX Run4 Au+Au dataset. It uses strict particle identification(PID) in the Electromagnetic Calorimeter(EMCal) and a charged particle veto to extract a clean photon signal. These photons are then tagged with EMCal photon candidates with loose PID cuts, which can be reconstructed with high efficiency, to determine the fraction of photons originating from $\pi^{0}$ decays. Many systematic uncertainties and detector effects cancel in this method.