Electromagnetic radiation as a probe of the initial state and of viscous   dynamics in relativistic nuclear collisions
  The penetrating nature of electromagnetic signals makes them suitable probes to explore the properties of the strongly-interacting medium created in relativistic nuclear collisions. We examine the effects of the initial conditions and shear relaxation time on the spectra and flow coefficients of electromagnetic probes, using an event-by-event 3+1D viscous hydrodynamic simulation (MUSIC). 
Gojko Vujanovic, Jean-Fran\c{c}ois Paquet, Gabriel S. Denicol, Matthew   Luzum, Sangyong Jeon, and Charles Gale
nucl-th hep-ph nucl-ex