The box anomaly and radiative decays of η(η')-mesons

Abstract

We report on a confined quark model calculation of the transition form factors for the radiative decays of η(η')->γl^+l^- and η(η')->γπ^+π^-. The η-η' mixing angle θ_P is determined from the set of data on the electromagnetic η(η') decays. It is found that θ_P\sim -16.5. The analysis of the dipionic mass distribution in the decay η'->γπ^+π^- confirms the existence of a non-resonant contribution which is the box anomaly.