Speaker
Aleksey Sibidanov
(Budker Institute of Nuclear Physics (BINP))
Description
We present measurements of exclusive and inclusive semileptonic $B_s$ decays using 121 $\rm{fb}^{-1}$ of data collected with the Belle detector near the $\Upsilon(5S)$ resonance. The inclusive branching fraction ${\cal B}(B_s \to X^- \ell^+ \nu_\ell)$ is measured in a sample enhanced in $B_s^{(*)0}\bar{B}_s^{(*)0}$ pair events by reconstructing a tag $D_s^+$ meson. The signal lepton $\ell^+ = e^+,\mu^+$ is required to be of the same-sign charge as the tag $D_s^+$ meson to ensure that both stem from different $B_s^0$ mesons. The branching fraction is extracted by comparing the ratio of measured $D_s^+$ and $D_s^+\ell^+$ yields to known production and branching fractions. The exclusive decays $B_s^0 \to D_s^{(*)-} \ell^+ \nu_\ell$ are studied in events where a lepton candidate $\ell^+$ is paired with a $D_s^-$ of the opposite-sign charge. We exploit the knowledge of the collision energy to identify signal decays based on the zero mass hypothesis for the unreconstructed neutrino.
Primary author
Prof.
Youngjoon Kwon
(Yonsei University)
