Speaker
Description
Precise determination of the magnitudes and phases of the elements, in particular, $V_{ub}$ and $V_{cb}$, of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is crucial for testing the unitarity of the CKM matrix, hence testing the Standard Model. The magnitudes of these elements are best measured by using $B$-meson semileptonic decays. Moreover, semileptonic $B$-meson decays provide a great testing ground for lepton universality of charged-current weak interaction processes. In this talk, we report recent unique and/or competitive results of inclusive and exclusive $B$-meson semileptonic decays, which have been measured by analyzing high-statistics data sample of $B\bar{B}$ pairs from the Belle and Belle II experiments. Some of these analyses utilize tag-side reconstruction of a companion $B$-meson decaying into hadronic final states, providing direct access to the signal $B$ rest-frame and the relevant decay characteristics. The subjects we present in this talk are all relevant for either testing lepton universality or precision measurement of the CKM elements $|V_{cb}|$ and $|V_{ub}|$.
