eta ' -> pi(0)gamma gamma and eta ' -> eta gamma gamma: a primer analysis

The electromagnetic rare decays eta' -> pi(0)gamma gamma and eta' -> pi(0)gamma gamma are analysed for the first time and their predicted branching ratios given. The vector meson exchange dominant contribution is treated using Vector Meson Dominance and the scalar component is estimated by means of the Linear Sigma Model. The agreement between our calculation and the measurement of the related process eta' -> pi(0)gamma gamma is a check of the procedure. Scalar meson effects are seen to be irrelevant for eta' -> pi(0)gamma gamma while a significant scalar contribution due to the sigma(500) resonance seems to emerge in the case of eta' -> pi(0)gamma gamma. Future measurements coming from KLOE-2, Crystal Ball, WASA, and BES-III will elucidate if any of these processes carry an important scalar contribution or they are simply driven by the exchange of vector mesons.