Radiative decays, photoproduction and total cross section of the ψ particles

Abstract

It is pointed out that the coupling characterizing the ψ-γ vertex must change substantially between the limits, ψ on mass-shell which occurs in ψ→e ⁺ e⁻ and photon on mass-shell which is relevant in radiative decays like ψ→ππ γ, ψ→η γ and photoproduction of ψ. This has the consequence that the value of ψ N total cross section must be larger than what is inferred from the use of naive vector dominance in photoproduction.