The $\sigma $ pole in $J/\psi \to \omega \pi^+ \pi^-$

TL;DR

This paper analyzes the decay of $J/ar{J}$ into $ ext{omega} ext{pi}^+ ext{pi}^-$ using a large data sample, identifying the $\sigma$ pole position and other resonant signals.

Contribution

It provides a precise determination of the $\sigma$ meson pole position from $J/ar{J}$ decay data, improving understanding of light scalar mesons.

Findings

Observation of a broad $\sigma$ peak at low $ ext{pi} ext{pi}$ mass

Determination of the $\sigma$ pole position as $(541 ext{MeV} ext{ - } i 252 ext{MeV})$

Identification of $ ext{omega} f_2(1270)$ and $b_1(1235) ext{pi}$ signals

Abstract

Using a sample of 58 million $J/\psi$ events recorded in the BESII detector, the decay $J/\psi \to \omega \pi^+ \pi^-$ is studied. There are conspicuous $\omega f_2(1270)$ and $b_1(1235)\pi$ signals. At low $\pi \pi$ mass, a large broad peak due to the $\sigma$ is observed, and its pole position is determined to be $(541 \pm 39) $ - $i$ $(252 \pm 42)$ MeV from the mean of six analyses. The errors are dominated by the systematic errors.