The gVσγ coupling constants in hadron electrodynamics Original Research Article

Recent measurements of the branching ratios for the decays ω→π0π0γ and ρ0→π0π0γ lead to coupling constants of the Vσγ interaction (V is a vector meson) one order of magnitude smaller than previously assumed to describe the threshold cross section of γ+p→p+ρ0 and the HERMES effect. The new g2Vσγ couplings are in contradiction with the predictions of the QCD sum rules, but are in agreement with vector meson dominance estimation of the σ→γγ width.