Internal conversion of pseudoscalar mesons into lepton pairs

The Kroll-Wada formulation of the internal conversion of mesons into lepton pairs is modified by taking into account the correction due to the effect of exchange of leptons. Single- and double-pair decays, such as π⁰(K_L, η)→e⁺e⁻γ, K_L(η)→μ⁺μ⁻γ, π⁰(K_L, η)→e⁺e⁻e⁺e⁻, and K_L(η)→μ⁺μ⁻μ⁺μ⁻, are studied under the assumption of CP invariance. A spectral analysis is made, stressing the importance of this exchange effect in the shape of the spectra. These kinds of experiments are proposed as a clue to obtain knowledge about the meson-photon-photon vertices.