Photon production throughA1resonance in high-energy heavy-ion collisions

Electromagnetic radiation from excited hadronic matter is one of the best ways to study the properties of matter. Considering various processes in the hadronic gas, Kapusta, Lichard, and Seibert have found a $\pi \rho \to \pi \gamma$ reaction with an intermediate virtual $\pi$ or $\rho$ to be the main source of photons with energy greater than 0.7 GeV. However, at temperatures considered, $T=100\mathrm{}-200$ MeV, a $\pi \rho$ pair can easily form an $A_1\mathrm{}\left(1260\right)\mathrm{}$ resonance, and we show that this mechanism leads to photon production rates exceeding those suggested previously.