Electromagnetic Corrections in Two-Photon Decays of π0, η, and η' Mesons

The role of electromagnetic corrections in anomalous decays $${{\pi }^{0}},\eta ,\eta ' \to \gamma \gamma $$ is investigated. To obtain the amplitudes of these processes, effective Lagrangian of the $$1{\text{/}}{{N}_{c}}$$ chiral perturbation theory is used; analysis is confined to the vertices appearing at the first two steps of the $$1{\text{/}}{{N}_{c}}$$ expansion. It is shown that the inclusion of electromagnetic interactions leads to corrections ensuring full agreement between theoretical estimates of decay widths and experimental data. The effects caused by isospin and unitary symmetry breaking are considered in detail against the general background of predominance of contributions from non-Abelian and gluon anomalies.