A tale of tails: Photon rates and flow in ultra-relativistic heavy ion collisions

We consider the possibility that quark and gluon distributions in the medium created in high energy heavy ion collisions may be modified by a power law tail at energies much higher than the temperature. We parametrize such a tail by Tsallis distributions with an exponent motivated by phenomenology. These distributions are characterized by an effective temperature scale that we assume to evolve in time like the temperature for thermal distributions. We find that including such a tail increases the rates for photon production and significantly delays the emission times for photons of a fixed energy. We argue that these effects should modify photon yields and flow patterns in a way that will help the agreement of theoretical calculations with data from LHC and RHIC experiments. (C) 2015 Elsevier B.V. All rights reserved.