Semileptonic and Leptonic $B$ Physics at Belle II

Abstract

Semileptonic decays of $B$ mesons that proceed via $b\rightarrow u$ and $b\rightarrow c$ transitions, as well as rare leptonic $B$ decays, are fertile grounds for probing new physics beyond the Standard Model. The Belle II experiment presents as an excellent opportunity to study such decays, and since beginning operation in 2019, Belle II has already recorded half of the data collected by its predecessor and reached an instantaneous luminosity greater than $4\times 10^{34}$ cm$^{-2}$s$^{-1}$. Belle II expects to explore flavour physics with $B$ and charmed mesons with unprecedented precision, and has already produced multiple world-leading results in this area. We present recent results from Belle II on measurements of the CKM parameters $V_{ub}$ and $V_{cb}$ as well as results for $R(X_{e/\mu})$.