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. $\eta_c (\eta_c')\to VV$. 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 $\eta_c'$ are the spin-0 partners of $J/\psi$ and $\psi'$, 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".