Direct photon measurements in He+Au collisions at 200 GeV

The PHENIX experiment has published direct photon yields from different collisions at RHIC energies and discovered a large excess of low-p_T direct photons in Au+Au collisions at $\sqrt{{}^{s}NN}=200$ GeV compared to reference p+p collisions, which has been attributed to thermal radiation from the hot and dense medium. PHENIX has also developed a new technique to identify conversion photons without assuming the radius where the conversion happened. This method greatly increases the available statistics and reduces systematic uncertainties. This paper presents the results obtained from real photons in the electromagnetic calorimeter and photons converted at the layers of Silicon Vertex Tracker (VTX). (paper)