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

TL;DR

This paper analyzes the $J/ar{ ext{psi}} o ar{ ext{pi}}^0 e^+ e^-$ decay using resonance chiral theory, highlighting the roles of strong and electromagnetic interactions in explaining the invariant mass spectrum and decay channels.

Contribution

It provides the first analysis of the electron-positron invariant mass spectrum in $J/ar{ ext{psi}}$ decays within resonance chiral theory, including form factors and decay ratios.

Findings

Both strong and electromagnetic interactions are essential for data description.

The $ ext{pi}^0$ transition form factor for $J/ar{ ext{psi}} o ext{pi}^0 ext{gamma}^*$ is obtained.

Decay channels $J/ar{ ext{psi}} o ext{pi}^0 ho^0$ are strong interaction dominated, others are electromagnetic dominated.

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.