Measurements of the cross sections for e+e−→hadrons at 3.650, 3.6648, 3.773 GeV and the branching fraction for ψ(3770)→non-DD¯

Using the BES-II detector at the BEPC Collider, we measured the lowest order cross sections and the R values (R=σe+e−→hadrons0/σe+e−→μ+μ−0) for inclusive hadronic event production at the center-of-mass energies of 3.650, 3.6648 and 3.773 GeV. The results lead to R¯uds=2.218±0.019±0.089 which is the average of these measured at 3.650 GeV and 3.6648 GeV, and R=3.746±0.037±0.187 at s=3.773GeV. We determined the lowest order cross section for ψ(3770) production to be σψ(3770)B=(9.323±0.253±0.801)nb at 3.773 GeV, the branching fractions for ψ(3770) decays to be BF(ψ(3770)→D0D¯0)=(49.5±1.3±3.8)%, BF(ψ(3770)→D+D−)=(35.7±1.1±3.4)% and BF(ψ(3770)→DD¯)=(85.5±1.7±5.8)%, which result in the total non-DD¯ branching fraction of ψ(3770) decay to be BF(ψ(3770)→non-DD¯)=(14.5±1.7±5.8)%.