Abstract
The electromagnetic rare decays η′ → π0γγ and η′ → π0γγ 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 → π0γγ is a check of the procedure. Scalar meson effects are seen to be irrelevant for η′ → π0γγ, while a significant scalar contribution due to the σ(500) resonance seems to emerge in the case of η′ → π0γγ. 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.
Highlights
From the experimental point of view, the electromagnetic rare decays η → π0γγ and η → ηγγ, which have not yet been observed, will be potentially measured at several experiments such as KLOE-2, Crystal Ball, WASA, and BES-III [1, 2], while the related η → π0γγ process, for which a measurement of its branching ratio and invariant mass spectrum already exists [3], will be certainly determined with higher precision
The electromagnetic rare decays η → π0γγ and η → π0γγ 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
Summary
From the experimental point of view, the electromagnetic rare decays η → π0γγ and η → ηγγ, which have not yet been observed, will be potentially measured at several experiments such as KLOE-2, Crystal Ball, WASA, and BES-III [1, 2], while the related η → π0γγ process, for which a measurement of its branching ratio and invariant mass spectrum already exists [3], will be certainly determined with higher precision. The chiral-loop prediction will be substituted by a Linear Sigma Model (LσM) calculation where the effects of scalar meson resonances are taken into account explicitly.
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