A consistent description of rho0 -> pi pi gamma decays including sigma(500) meson effects

Abstract

A consistent description of $\sigma(500)$ meson effects in $\rho^0\to\pi^0\pi^0\gamma$ and $\pi^+\pi^-\gamma$ decays is proposed in terms of reasonably simple amplitudes which reproduce the expected chiral-loop behaviour for large $m_{\sigma}$ values. For the neutral case, in addition to the well known $\omega$ exchange, there is an important contribution from the $\sigma(500)$ meson that is in agreement with recent experimental data. For the charged case, where the dominant contribution comes from bremsstrahlung, the effects of the $\sigma(500)$ meson are relevant only at high values of the photon energy and compatible with present data. A combined analysis of both processes with moderately improved experimental information should contribute decisively to clarify the status of this controversial $\sigma(500)$ meson.