Updated study of the $η_c$ and $η_c^\prime$ decays into light vector mesons

We re-investigate the exclusive decays of $η_c$ and $η_c^\prime$ to a pair of light vector mesons, i.e. $η_c (η_c')\to VV$. 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 $η_c$ and $η_c'$ are the spin-0 partners of $J/ψ$ and $ψ'$, respectively, our study is useful for gaining insights into the pQCD helicity selection rule violations in charmonium decays and the long-standing "$ρπ$ puzzle".

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