Measurements of the branching fractions for $B\to K^{\ast }{\hat{I}}^3$ decays at Belle II

Abstract

This paper reports a study of $B\to K^{\ast }{\hat{I}}^3$ decays using $62.8\pm 0.6$ fb${}^{-1}$ of data collected during 2019--2020 by the Belle II experiment at the SuperKEKB $e^{+}{e}^{-}$ asymmetric-energy collider, corresponding to $(68.2\pm 0.8)\times 10^6$ $B\overline{B}$ events. We find $454\pm 28$, $50\pm 10$, $169\pm 18$, and $160\pm 17$ signal events in the decay modes $B^0\to K^{\ast 0}[K^{+}\ddot{I}{€}^{-}]{\hat{I}}^3$, $B^0\to K^{\ast 0}[K_{\mathrm{S}}^0\ddot{I}{€}^0]{\hat{I}}^3$, $B^{+}\to K^{\ast +}[K^{+}\ddot{I}{€}^0]{\hat{I}}^3$, and $B^{+}\to K^{\ast +}[K^{+}\ddot{I}{€}^0]{\hat{I}}^3$, respectively. The uncertainties quoted for the signal yield are statistical only. We report the branching fractions of these decays: $$\mathcal{B}[B^0\to K^{\ast 0}[K^{+}\ddot{I}{€}^{-}]{\hat{I}}^3]=(4.5\pm 0.3\pm 0.2)\times 10^{-5},$$ $$\mathcal{B}[B^0\to K^{\ast 0}[K_{\mathrm{S}}^0\ddot{I}{€}^0]{\hat{I}}^3]=(4.4\pm 0.9\pm 0.6)\times 10^{-5},$$ $$\mathcal{B}[B^{+}\to K^{\ast +}[K^{+}\ddot{I}{€}^0]{\hat{I}}^3]=(5.0\pm 0.5\pm 0.4)\times 10^{-5},\text{ and}$$ $$\mathcal{B}[B^{+}\to K^{\ast +}[K_{\mathrm{S}}^0\ddot{I}{€}^{+}]{\hat{I}}^3]=(5.4\pm 0.6\pm 0.4)\times 10^{-5},$$ where the first uncertainty is statistical, and the second is systematic. The results are consistent with world-average values.