Study of electromagnetic decay of $J/\psi$ and ${\psi }^{\prime }$ to vector and pseudoscalar

Abstract

The electromagnetic decay contributions to $J/\psi ({\psi }^{\prime })\to VP$, where $V$ and $P$ stand for vector and pseudoscalar meson, respectively, are investigated in a vector meson dominance (VMD) model. We show that $J/\psi ({\psi }^{\prime })\to {\gamma }^{\ast }\to VP$ can be constrained well with the available experimental information. We find that this process has significant contributions in ${\psi }^{\prime }\to VP$ and may play a key role in understanding the deviations from the so-called "12% rule" for the branching ratio fractions between ${\psi }^{\prime }\to VP$ and $J/\psi \to VP$. We also address that the "12% rule" becomes very empirical in exclusive hadronic decay channels.

Comments: Revtex, 10 pages, 1 eps figure; further discussions about the helicity conservation rule and exp. constraints are included; version to appear in Phys. Lett. B