Measurements of the continuum $R_{\rm uds}$ and $R$ values in $e^+e^-$ annihilation in the energy region between 3.650 and 3.872 GeV

Abstract

We report measurents of the continuum $R_{\rm uds}$ near the center-of-mass energy of 3.70 GeV, the $R_{{\rm uds(c)}+ψ(3770)}(s)$ and the $R_{\rm had}(s)$ values in $e^+e^-$ annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collodier. We obtain the $R_{\rm uds}$ for the continuum light hadron (containing u, d and s quarks) production near the $D\bar D$ threshold to be $R_{\rm uds}=2.141 \pm 0.025 \pm 0.085$.