Semi-inclusive studies of semileptonic $B_s$ decays at Belle

Abstract

We present an analysis of the semi-inclusive decays $B_s\to D_s^{-}X{\ell }^{+}\hat{I}½$ and $B_s\to D_s^{\ast -}X{\ell }^{+}\hat{I}½$, where $X$ denotes a final state that may consist of additional hadrons or photons and $\ell$ is an electron or muon. The studied $B_s$ decays are contained in the $121.4{\mathrm{fb}}^{-1}$ $\hat{I}\yen (5S)$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The branching fractions of the decays are measured to be $\mathcal{B}(B_s\to D_s^{-}X{\ell }^{+}\hat{I}½)=[8.2\pm 0.2(\text{stat})\pm 0.6(\text{syst})\pm 1.4(\text{ext})]\%$ and $\mathcal{B}(B_s\to D_s^{\ast -}X{\ell }^{+}\hat{I}½)=[5.4\pm 0.4(\text{stat})\pm 0.4(\text{syst})\pm 0.9(\text{ext})]\%$, where the first two uncertainties are statistical and systematic and the last is due to external parameters. The measurement also provides an estimate of the $B_s^{(\ast )}{\bar{B}}_s^{(\ast )}$ production cross-section, $\ddot{I}ƒ(e^{+}{e}^{-}\to B_s^{(\ast )}{\bar{B}}_s^{(\ast )})=(53.8\pm 1.4(\text{stat})\pm 4.0(\text{syst})\pm 3.4(\text{ext}))\mathrm{pb}$, at the center-of-mass energy $\sqrt{s}=10.86\mathrm{GeV}$.

13 pages, 2 figures, submitted to Phys. Rev. D