An anlaysis on $J/\psi\to\pi^0\gamma^*$ within resonance chiral theory

Abstract

In this study, we analyze the first measurement of the electron-positron invariant mass spectrum in $J/\psi \to \pi^0 e^+e^-$ by BESIII, using the framework of resonance chiral theory. Our results indicate that both strong interaction and electromagnetic transition are essential to accurately describe the data. We obtain the $\pi^0$ transition form factor for $J/\psi \to \pi^0\gamma^*$ and the corresponding decay branching ratios for $J/\psi \to \pi^0 l^+l^-$. The decay process $J/\psi \to \pi^0 V$ is also examined. It is found that $J/\psi \to \pi^0 \rho^0$ is dominated by the strong interaction, while the other two channels, $J/\psi \to \pi^0 \omega$ and $\pi^0 \phi$, arise primarily from electromagnetic transitions.