Qi-Dong Zhou

09 February 2023
7th KEK Flavour-Factory Workshop

Abstract: Measurement of branching ratio $R(D^{*})$ of $B \rightarrow D^{*} \tau \nu_{\tau}$ relative to $B \rightarrow D^{*} \ell \nu_{\ell}$ decays with hadronic tagging is performed by using data sample of $198 \times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle~II detector at the SuperKEKB asymmetric-energy $e^{+}e^{-}$ collider. The analysis uses hadronic reconstruction of the tag-side $B$ meson based on Full Event Interpretation technique and purely leptonic $\tau$ decays on signal-side $B$ meson. We will report the methodology and expected sensitivity, as well as part of the expected systematic uncertainty. language: