Direct measurement of the cross sections for D0D¯0, D+D− and DD¯ production by e+e− annihilation at the center-of-mass energy s=3.773 GeV

The cross sections for D0D¯0, D+D− and DD¯ production by e+e− annihilation at the center-of-mass energy s=3.773 GeV have been directly measured with the BES-II detector at the BEPC collider. The measurement of the cross sections is made by analyzing both the singly tagged D events and the doubly tagged DD¯ events from the data sample of about 17.3 pb−1 collected at s=3.773 GeV. The observed cross sections are σD0D¯0obs=(3.47±0.32±0.21) nb, σD+D−obs=(2.46±0.33±0.20) nb and σDD¯obs=(5.93±0.46±0.35) nb, which correspond to the tree level cross sections to be σD0D¯0=(4.45±0.41±0.32) nb, σD+D−=(3.16±0.42±0.28) nb and σDD¯=(7.61±0.59±0.54) nb, respectively.