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

Understand

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".