Preliminary results on direct photon-photon HBT measurements in square root sNN = 62.4 GeV and 200 GeV Au+Au collisions at RHIC

We present the preliminary results on direct photon interferometry measurements in Au+Au collisions at square root sNN = 62.4 GeV and 200 GeV using the STAR (solenoidal tracker at RHIC) detector. Photons are reconstructed via e+/e- conversions in STAR Time Projection Chamber (TPC) and energy deposited by photons in STAR Barrel Electromagnetic Calorimeter (BEMC). The two-photon correlations are measured using (1) both photons measured with BEMC; (2) one photon from conversions and the other measured with BEMC. Both the methodologies and the possible constraints in the correlation function measurements are discussed.