Observation of the $B_s^0 \rightarrow D^{\ast \pm} D^{\mp}$ decay

TL;DR

This paper reports the first observation of the decay $B_s^0 ightarrow D^{* ext{±}} D^{ ext{∓}}$ using LHCb data, measuring its branching fraction relative to a similar decay with high significance.

Contribution

The study provides the first observation and measurement of the $B_s^0 ightarrow D^{* ext{±}} D^{ ext{∓}}$ decay, expanding knowledge of B meson decay modes.

Findings

Decay observed with high significance

Branching fraction ratio measured as 0.137

Uncertainties include statistical, systematic, and hadronisation ratio

Abstract

A search for the $B^0_s \!\rightarrow D^{*\pm} D^\mp$ decay is performed using proton-proton collision data at centre-of-mass energies of $7$, $8$ and $13\,\text{TeV}$ collected by the LHCb experiment, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. The decay is observed with a high significance and its branching fraction relative to the $B^0 \!\rightarrow D^{*\pm} D^\mp$ decay is measured to be \begin{align*} \frac{\mathcal{B}(B_s^0 \rightarrow D^{\ast \pm} D^{\mp}) }{\mathcal{B}(B^0 \rightarrow D^{\ast \pm} D^{\mp}) } = 0.137 \pm 0.017 \pm 0.002 \pm 0.006 \,, \end{align*} where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the $B_s^0$ and $B^0$ hadronisation fractions.