Thermal photons from $\pi\rho \ra \pi\gamma$ revisited

Abstract

We evaluate the photon spectra from the reaction $\pi\rho\ra \pi\gamma$ for the exchange of $\pi$, $\rho$, $\omega$, $\phi$ and $a_1$ as intermediary mesons. It is found that the contributions from the intermediary $a_1$ is more than any other meson exchange processes up to photon energies 2.5 GeV.