Event-by-event direct photon anisotropic flow in relativistic heavy-ion collisions

C. Shen, J. F. Paquet, J. Liu, G. Denicol, U. Heinz and C. Gale,  arXiv:1407.8533 [nucl-th]

Abstract: We consider directly emitted and hadronic decay photons from event-by-event hydrodynamic simulations. We compute the direct photon anisotropic flow coefficients and compare with recent experimental measurements. We find that it is crucial to include the photon multiplicity as a weighting factor in the definition of vγn. We also investigate the sensitivity of the direct photon spectrum and elliptic flow to the theoretical uncertainty of the photon emission rate in the quark-hadron transition region and to the pre-equilibrium dynamics of relativistic heavy-ion collisions.