Study of Scalar Mesons at BES

TL;DR

This paper analyzes BES data to study scalar mesons, identifying several states and their properties, including the $0(980)$, $0(1370)$, $0(1710)$, and $0(1790)$, with detailed pole positions and parameters.

Contribution

It provides new measurements of scalar meson parameters and evidence for multiple scalar states, including the $0(1790)$, using partial wave analysis of BES data.

Findings

Evidence for $0(980)$, $0(1370)$, $0(1710)$, and $0(1790)$ mesons.

Precise pole positions for $0(980)$ and $0(540)$ states.

Parameters of the Flatté formula for $0(980)$.

Abstract

Partial wave analyses have been performed on BES data to study scalar mesons. There is evidence for the $\kappa$ near the $K\pi$ threshold and the pole position is $(760\sim840) -$i$(310\sim 420)$ MeV. The $\sigma$ peak is seen in $\omega\pi^+\pi^-$ and gives an accurate pole position, $(541\pm39)-$i$(252\pm42)$ MeV. The $f_0(980)$ is seen in both $\phi \pi^+\pi^-$ and $\phi K^+K^-$ data. Parameters of the Flatt\' e formula for $f_0(980)$ are: $M = 965 \pm 8(sta) \pm 6(sys) $ MeV, $g_1 = 165 \pm 10(sta) \pm 15(sys)$ MeV, $g_2/g_1 = 4.21 \pm 0.25(sta) \pm 0.21(sys)$. The $J/\psi\to \phi \pi^+\pi^-$ data require $f_0(1790)\to\pi^+\pi^-$, distinct from $f_0(1710)\to K^+K^-$. Also $f_0(1370)$ is seen clearly in $\phi \pi^+\pi^-$ data.