Flavour changing charged current decays at LHCb

TL;DR

This paper reports recent LHCb measurements testing the Standard Model's lepton universality through semileptonic $b$-hadron decays, providing insights into potential New Physics effects.

Contribution

It presents three new results from LHCb: a ratio of branching fractions, a branching fraction measurement, and form-factor parameters extraction, advancing tests of the SM.

Findings

First measurement of $ (D^{**})$ ratio using $B^{-} o D^{**0} au^{-} ar{ u}_{ au}$ decays

Determined the branching fraction for $ Lambdato p \mu^{-} ar{ u}_{}$

Extracted form-factor parameters from $B^0 o D^{*-} \mu^{+} u_{e}$ decays

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.