Measurement of the branching fraction of the decay $B^{-}\to D^0\ddot{I}(770{)}^{-}$ at Belle II

Abstract

We measure the branching fraction of the decay $B^{-}\to D^0\ddot{I}(770{)}^{-}$ using data collected with the Belle II detector. The data contain 387 million $B\overline{B}$ pairs produced in $e^{+}{e}^{-}$ collisions at the $\hat{I}\yen (4S)$ resonance. We reconstruct $8360\pm 180$ decays from an analysis of the distributions of the $B^{-}$ energy and the $\ddot{I}(770{)}^{-}$ helicity angle. We determine the branching fraction to be $(0.939\pm 0.021(\mathrm{stat})\pm 0.050(\mathrm{syst}))\%$, in agreement with previous results. Our measurement improves the relative precision of the world average by more than a factor of two.