Flavour changing charged current decays at LHCb

Abstract

The Standard Model (SM) predicts the universality of lepton couplings with the electroweak gauge bosons. Semileptonic decays of $b$-hadrons provide a powerful framework for testing the SM and probing possible New Physics effects. In particular, the processes mediated by charged-current interactions benefit from a relatively large branching fractions and theoretically well-controlled hadronic matrix elements. This contribution presents three recent results from the LHCb experiment: the first measurement of the ratio of branching fractions $\mathcal{R}(D^{**})$ using $B^{-} \to D^{**0} \tau^{-} \bar{\nu}_{\tau}$ decays, the determination of the branching fraction for $\Lambda \to p \mu^{-} \bar{\nu}_{\mu}$ and the extraction of form-factor parameters from $B^0 \to D^{*-} \mu^{+} \nu_{\mu}$ decays.