Photon Production from Nonequilibrium Disoriented Chiral Condensates in   a Spherical Expansion
  We study the production of photons through the non-equilibrium relaxation of a disoriented chiral condensate formed in the expanding hot central region in ultra-relativistic heavy-ion collisions. It is found that the expansion smoothes out the resonances in the process of parametric amplification such that the non-equilibrium photons are dominant to the thermal photons over the range 0.2-2 GeV. We propose that to search for non-equilibrium photons in the direct photon measurements of heavy-ion collisions can be a potential test of the formation of disoriented chiral condensates. 
Yeo-Yie Charng, Kin-Wang Ng, Chi-Yong Lin, Da-Shin Lee