Angular analysis of the $e^{+}{e}^{-}\to D^{(\ast )\pm }{D}^{\ast \mp }$ process near the open charm threshold using initial-state radiation

Abstract

We report a new measurement of the exclusive $e^{+}{e}^{-}\to D^{(\ast )\pm }{D}^{\ast \mp }$ cross sections as a function of the center-of-mass energy from the $D^{(\ast )\pm }{D}^{\ast \mp }$ threshold through $\sqrt{s}=6.0$ GeV with initial-state radiation. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of $951$ fb${}^{-1}$. The accuracy of the cross section measurement is increased by a factor of two over the first Belle study. We perform the first angular analysis of the $e^{+}{e}^{-}\to D^{\ast \pm }{D}^{\ast \mp }$ process and decompose this exclusive cross section into three components corresponding to the $D^{\ast }$ helicities.

23 pages, 21 figures, 3 tables. Submitted to PRD