Study of the reaction $e^+e^- \to \pi^0\gamma$ with the SND detector at the VEPP-2M collider

TL;DR

This study measures the cross section of the process $e^+e^- o ext{pi}^0 ext{gamma}$ across a range of energies, determines branching fractions for vector mesons, and confirms the vector meson dominance model with high precision.

Contribution

It provides the most accurate measurements to date of the $e^+e^- o ext{pi}^0 ext{gamma}$ process and extracts key meson decay parameters using the vector meson dominance model.

Findings

Measured cross section from 0.60 to 1.38 GeV

Determined branching fractions for $ ho$, $ extomega$, and $ extphi$ mesons

Confirmed the vector meson dominance model

Abstract

The process $e^+e^- \to \pi^0\gamma$ has been studied in the experiment with the SND detector at the VEPP-2M $e^+e^-$ collider. The $e^+e^- \to \pi^0\gamma$ cross section has been measured in the center-of-mass energy range from 0.60 to 1.38 GeV. The cross section is well described by the vector meson dominance model. From the fit to the cross section data we have determined the branching fractions $B(\rho\to\pi^0\gamma)=(4.20\pm0.52)\times10^{-4}$, $B(\omega\to\pi^0\gamma)=(8.88\pm0.18)\%$, $B(\phi\to\pi^0\gamma)=(1.367\pm0.072)\times10^{-3}$, and the relative phase between the $\rho$ and $\omega$ amplitudes $\varphi_{\rho}=(-12.7\pm4.5)^\circ$. Our data on the process $e^+e^- \to \pi^0\gamma$ are the most accurate to date.