Probing the early-time dynamics of relativistic heavy-ion collisions   with electromagnetic radiation
  Using 3+1D viscous relativistic fluid dynamics, we show that electromagnetic probes are sensitive to the initial conditions and to the out-of-equilibrium features of relativistic heavy-ion collisions. Within the same approach, we find that hadronic observables show a much lesser sensitivity to these aspects. We conclude that electromagnetic observables allow access to dynamical regions that are beyond the reach of soft hadronic probes. 
Gojko Vujanovic, Jean-Francois Paquet, Gabriel S. Denicol, Matthew   Luzum, Bjoern Schenke, Sangyong Jeon, and Charles Gale
hep-ph nucl-ex nucl-th