Further insights into the "$\rho\pi$ puzzle"

TL;DR

This paper investigates the mechanisms behind the $ ho ext{ extpi}$ puzzle in $J/\psi$ and $\psi^\prime$ decays, highlighting the roles of electromagnetic and meson loop transitions in explaining the observed decay patterns.

Contribution

It offers a comprehensive analysis of electromagnetic and meson loop effects, providing a coherent explanation for the $ ho ext{ extpi}$ puzzle in charmonium decays.

Findings

Electromagnetic transitions cause significant interference in $\psi^\prime o ho ext{ extpi}$ decays.

Intermediate meson loops induce destructive interference, affecting decay rates.

A unified understanding of the $ ho ext{ extpi}$ puzzle is achieved through these mechanisms.

Abstract

Based on a systematic investigation of $J/\psi(\psi^\prime)\to VP$, where $V$ and $P$ stand for light vector and pseudoscalar mesons, we identify the role played by the electromagnetic (EM) transitions and intermediate meson loop transitions, which are essential ingredients for understanding the $J/\psi$ and $\psi^\prime$ couplings to $VP$. We show that on the one hand, the EM transitions have relatively larger interferences in $\psi^\prime\to \rho\pi$ and $K^*\bar{K}+c.c.$ as explicitly shown by vector meson dominance (VMD). On the other hand, the strong decay of $\psi^\prime$ receives relatively larger destructive interferences from the intermediate meson loop transitions. By identifying these mechanisms in an overall study of $J/\psi(\psi^\prime)\to VP$, we provide a coherent understanding of the so-called "$\rho\pi$ puzzle".