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

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We report a new measurement of the exclusive $e^+ e^- \to D^{(*) \pm} D^{*\mp}$ cross sections as a function of the center-of-mass energy from the $D^{(*) \pm} D^{* \mp}$ 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 $e^+ e^- \to D^{* \pm} D^{* \mp}$ process and decompose this exclusive cross section into three components corresponding to the $D^*$ helicities.