The Semileptonic B Frontier: LHC, B-factories, Lattice QCD & the Hunt for Precision

Abstract

This review document summarizes the main outcomes and key theoretical and experimental developments discussed at the workshop ``The Semileptonic $B$ Frontier: LHC, $B$-Factories, Lattice QCD & the Hunt for Precision'', held at Laboratori Nazionali di Frascati on 16--18 February, https://agenda.infn.it/event/49469/. Bringing together experimentalists and theorists, the meeting addressed recent advances and outstanding challenges in both charged-current ($b \to c/u\,\ellν$) and neutral-current ($b \to s\,\ell^+\ell^-$) semileptonic $b$-hadron decays. We synthesize current experimental measurements from Belle, Belle~II, and LHCb with state-of-the-art theoretical inputs---including Lattice QCD determinations, Heavy Quark Expansion (HQE) frameworks, and QED radiative corrections. In addition to reviewing the status of CKM matrix elements, hadronic form factor extractions, and Lepton Flavor Universality (LFU) tests, this report highlights novel observables and fitting techniques designed to maximize the sensitivity of future analyses and guide upcoming data-taking campaigns.