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

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