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

TL;DR

This study re-examines the decays of $ ext{eta}_c$ and $ ext{eta}_c'$ into light vector mesons, incorporating non-perturbative effects to better understand charmonium decay mechanisms and related puzzles.

Contribution

It introduces a combined analysis of short-distance and long-distance effects in $ ext{eta}_c$ and $ ext{eta}_c'$ decays, providing new insights into decay dynamics and pQCD rule violations.

Findings

Both decay processes are well constrained by experimental data.

Long-distance meson loop effects are significant in decay mechanisms.

Results shed light on the $ ho ext{pi}$ puzzle and helicity rule violations.

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".