Production of thermal photons in a simple chiral-hydrodynamic model
  We use a self-consistent chiral-hydrodynamic formalism which combines the linear $\sigma$ model with second-order hydrodynamics in 2+1 dimensions to compute the spectrum of thermal photons produced in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The temperature-dependent shear viscosity of the model, $\eta$, is calculated from the linearized Boltzmann equation. We compare the results obtained in the chiral-hydrodynamic model to those obtained in the second-order theory with a Lattice QCD equation of state and a temperature-independent value of $\eta/s$. We find that the thermal photon production is significantly larger in the latter model due to a slower evolution and larger dissipative effects. 
J. Peralta-Ramos, M. S. Nakwacki
hep-ph