Measurement of ${\mathcal B}$($B_s \rightarrow D_s X$) with $B_s$ Semileptonic Tagging

TL;DR

This paper presents the first direct measurement of the inclusive branching fraction of $B_s$ mesons decaying to $D_s X$ using semileptonic tagging in $e^+e^-$ collisions at the $$(5S) resonance, providing key insights into $B_s$ decay properties.

Contribution

It introduces a novel semileptonic tagging method to measure the inclusive $B_s ightarrow D_s X$ branching fraction directly in $e^+e^-$ collisions at the $$(5S) resonance.

Findings

Measured ${ m{ extbf{ extit B}}}(B_s ightarrow D_s X)$ as (60.2 ± 5.8 ± 2.3)%

First direct measurement of this inclusive branching fraction

Utilized partial reconstruction of semileptonic decays in $e^+e^-$ collisions

Abstract

We report the first direct measurement of the inclusive branching fraction ${\mathcal B}(B_s \rightarrow D_s X)$ via $B_s$ tagging in $e^+e^-\to\Upsilon$(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays $B_s \rightarrow D_s X \ell \nu$, 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 $\Upsilon$(5S) resonance by the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider, we obtain ${\mathcal B}(B_s \rightarrow D_s X)$ = $(60.2 \pm 5.8 \pm 2.3)$\%, where the first uncertainty is statistical and the second is systematic.