Chiral loops and a0(980) exchange in φ→π0ηγ

The radiative φ→π0ηγ decay is discussed emphasizing the effects of the a0(980) scalar resonance which dominates the high values of the π0η invariant mass spectrum. In its lowest part, the proposed amplitude coincides with the reliable and ChPT-inspired contribution coming from chiral loops. The a0(980) resonance is then incorporated exploiting the complementarity between ChPT and the linear sigma model for this channel. The recently reported experimental invariant mass distribution and branching ratio can be satisfactorily accommodated in our framework. For the latter, a value of B(φ→π0ηγ) in the range (0.75–0.95)×10−4 is predicted.