Measurement of $\mathcal{B}$($B_s\to D_{s}X$) with $B_s$ Semileptonic Tagging

Abstract

We report the first direct measurement of the inclusive branching fraction $\mathcal{B}(B_s\to D_{s}X)$ via $B_s$ tagging in $e^{+}{e}^{-}\to \hat{I}\yen$(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays $B_s\to D_{s}X\ell \hat{I}½$, where $X$ denotes unreconstructed additional hadrons or photons and $\ell$ is an electron or muon. With 121.4 fb${}^{-1}$ of data collected at the $\hat{I}\yen$(5S) resonance by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we obtain $\mathcal{B}(B_s\to D_{s}X)$ = $(60.2\pm 5.8\pm 2.3)$\%, where the first uncertainty is statistical and the second is systematic.