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.
Author
Prof.
Youngjoon Kwon
(Yonsei University)
