Recent Results on $\psi(3770)$ Physics at BES

TL;DR

This paper reports measurements of the $\psi(3770)$ resonance, including its non-$Dar D$ decay branching fraction, and observes an anomalous energy-dependent line shape in hadronic cross sections around 3.65 to 3.87 GeV, using BES-II data.

Contribution

It provides new measurements of $\psi(3770)$ decay modes and detailed line shape analyses, revealing unexpected features in the energy region near the resonance.

Findings

Measured the non-$Dar D$ decay branching fraction of $\psi(3770)$.

Observed an anomalous line shape in $ ext{e}^+ ext{e}^- o$ hadrons cross section.

Determined the production ratios of $D^+D^-$ and $D^0ar D^0$ near the resonance.

Abstract

There are about 33, 6.5 and 1.0 pb$^{-1}$ of $e^+e^-$ annihilation data have been taken around the center-of-mass energies of $\sqrt s=$ 3.773 GeV, at $\sqrt s=$ 3.650 GeV and at $\sqrt s=$ 3.6648 GeV, respectively, with the BES-II detector at the BEPC collider. By analyzing these data sets, we have measured the branching fraction for $\psi(3770)\to$ non-$D\bar D$ by several different methods; and have observed an anomalous line shape of $\sigma^{e^+e^-\to{\rm hadrons}}$ in energy region from 3.65 to 3.87 GeV; and have measured the line shapes of the $D^+D^-$, $D^0\bar D^0$ and $D\bar D$ production and together with the ratios of the production rates of $D^+D^-$ and $D^0\bar D^0$ in $e^+e^-$ annihilation around the $\psi(3770)$ resonance.