η′ →π⁰γγandη′ →ηγγ: a primer analysis

Abstract

Abstract. The electromagnetic rare decays η → π 0 γγ and η → π 0 γγ 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 η → π 0 γγ is a check of the procedure. Scalar meson effects are seen to be irrelevant for η → π 0 γγ, while a significant scalar contribution due to the σ(500) resonance seems to emerge in the case of η → π 0 γγ. 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.