Two-photon contributions toe+e−→ηγande+e−→η′γ

Abstract

Motivated by recent BABAR measurements of the {gamma}*{yields}{gamma}{eta} and {gamma}*{yields}{gamma}{eta}{sup '} transition form factors, we estimate two-photon exchange contributions to the corresponding cross sections. By using a phenomenological model, based on the vector meson dominance, it is argued that the expected contributions are small enough not to effect the BABAR results. As a by product we predict Br({eta}{sup '}{yields}{mu}{sup +}{mu}{sup -})=(1.4{+-}0.2)x10{sup -7}. Our results might be useful also in high precision calculations of radiative corrections to the Dalitz decays of pseudoscalar mesons.