Study of electromagnetic decay of J/ψJ/ψ and ψ′ψ′ to vector and pseudoscalar

The electromagnetic decay contributions to J/ψ(ψ′)→VPJ/ψ(ψ′)→VP, where V and P   stand for vector and pseudoscalar meson, respectively, are investigated in a vector meson dominance (VMD) model. We show that J/ψ(ψ′)→γ∗→VPJ/ψ(ψ′)→γ∗→VP can be constrained well with the available experimental information. We find that this process has significant contributions in ψ′→VPψ′→VP and may play a key role in understanding the deviations from the so-called “12% rule” for the branching ratio fractions between ψ′→VPψ′→VP and J/ψ→VPJ/ψ→VP. We also address that the “12% rule” becomes very empirical in exclusive hadronic decay channels.