Precison Measurements of the Mass, the Widths of $\psi(3770)$ Resonance and the Cross Section $\sigma[e^+e^-\to \psi(3770)]$ at $E_{\rm cm}=3.7724$ GeV

TL;DR

This paper precisely measures the properties of the $ ext{psi}(3770)$ resonance, including its mass, widths, and cross section, using $R$ values across a specific energy range, providing detailed resonance parameters.

Contribution

The study provides the most precise measurements to date of the $ ext{psi}(3770)$ resonance parameters and the continuum $R$ value in the energy region around 3.7 GeV.

Findings

Mass of $ ext{psi}(3770)$: 3772.4 MeV

Total width: 28.6 MeV

Observed cross section: 7.25 nb

Abstract

By analyzing the $R$ values measured at 68 energy points in the energy region between 3.650 and 3.872 GeV reported in our previous paper, we have precisely measured the mass, the total width, the leptonic width and the leptonic decay branching fraction of the $\psi(3770)$ to be ${M}_{\psi(3770)}=3772.4 \pm 0.4 \pm 0.3$ MeV, $\Gamma_{\psi(3770)}^{\rm tot} = 28.6 \pm 1.2 \pm 0.2$ MeV, $\Gamma_{\psi(3770)}^{ee} = 279 \pm 11 \pm 13$ eV and $B[\psi(3770)\to e^+e^-]=(0.98\pm 0.04\pm 0.04)\times 10^{-5}$, respectively, which result in the observed cross section $\sigma^{\rm obs}[e^+e^-\to \psi(3770)]=7.25\pm 0.27 \pm 0.34$ nb at $\sqrt{s}=3772.4$ MeV. We have also measured $R_{\rm uds}=2.121\pm 0.023 \pm 0.084$ for the continuum light hadron production in the region from 3.650 to 3.872 GeV.