The $g_{V\sigma\gamma}$-coupling constants in hadron electrodynamic

Abstract

Recent measurements of the branching ratios for the decays $\omega\to\pi^0\pi^0\gamma$ and $\rho^0\to\pi^0\pi^0\gamma$ lead to coupling constants of the $V\sigma\gamma$-interaction ($V$ is a vector meson) one order of magnitude smaller than previously assumed to describe the threshold cross section of $\gamma+p\to p+\rho^0$ and the HERMES effect. The new $g^2_{V\sigma\gamma}$ couplings are in contradiction with the predictions of the QCD sum rules, but are in good agreement with VDM-estimation of the $\sigma\to \gamma\gamma$-width.