On the two-photon contributions to $e^{+}{e}^{-}\to \eta \gamma$ and $e^{+}{e}^{-}\to {\eta }^{\prime }\gamma$

Abstract

Motivated by recent BABAR measurements of the ${\gamma }^{\ast }\to \gamma \eta$ and ${\gamma }^{\ast }\to \gamma {\eta }^{\prime }$ 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 $Br({\eta }^{\prime }\to {\mu }^{+}{\mu }^{-})=(1.4\pm 0.2)\times 10^{-7}$. Our results might be useful also in high precision calculations of radiative corrections to the Dalitz decays of pseudoscalar mesons.

Comments: 23 pages, LaTeX, needs FEYNMAN package