Updated study of the ${\eta }_c$ and ${\eta }_c^{\prime }$ decays into light vector mesons

Abstract

We re-investigate the exclusive decays of ${\eta }_c$ and ${\eta }_c^{\prime }$ to a pair of light vector mesons, i.e. ${\eta }_c({\eta }_c^{\prime })\to VV$. The long-distance intermediate meson loop (IML) effects are evaluated as a non-perturbative mechanism in addition to the short-distance $c\bar{c}$ annihilation contributions. We show that both processes can be reasonably well constrained with the help of the available experimental data. Since ${\eta }_c$ and ${\eta }_c^{\prime }$ are the spin-0 partners of $J/\psi$ and ${\psi }^{\prime }$, respectively, our study is useful for gaining insights into the pQCD helicity selection rule violations in charmonium decays and the long-standing "$\rho \pi$ puzzle".

Comments: 11 pages, 4 eps figures; Improved formulation based on 1010.1343[hep-ph]; Revised version accepted by Phys. Lett. B