Semileptonic B-decays at Belle and Belle II
Nikolai Peters
TL;DR
The work addresses precise determinations of CKM matrix elements $|V_{cb}|$ and $|V_{ub}|$ and tests of lepton flavor universality through semileptonic $B$ decays. It combines inclusive and exclusive approaches, employing tagging strategies such as Full Event Interpretation to maximize signal sensitivity and control backgrounds. Key contributions include new measurements of $R(D)$ and $R(D^*)$ with semileptonic tagging, inclusive $|V_{ub}|/|V_{cb}|$ and $|V_{ub}|$ determinations from Belle and Belle II, and a precise exclusive $|V_{cb}|$ from untagged $B\to D\ell\nu$ at Belle II using the Bourrely-Caprini-Lellouch parameterization. Overall, results are largely consistent with SM predictions within uncertainties and illustrate improved precision that will benefit CKM tests and constraints on new physics as Belle II collects more data.
Abstract
The paper summarizes recent results from the Belle and Belle II collaborations on semileptonic $B$ decays measurements including inclusive and exclusive determination of Cabibbo-Kobayashi-Maskawa matrix elements $|V_{cb}|$ and $|V_{ub}|$ and lepton flavor universality tests studies. The results are based on the full Belle data and 361 fb$^{-1}$ Belle II data samples collected in 2018 - 2022.