# Lepton flavour universality in charged-current $B$ decays

## TL;DR

This paper reviews recent experimental tests of lepton flavour universality in charged-current B decays, highlighting potential deviations from the Standard Model observed by LHCb, Belle, and BaBar collaborations.

## Contribution

It presents new measurements of al{R}(D^*) and al{R}(J/\u03psi) by LHCb, and al{R}(D) and al{R}(D^*) by Belle, updating the experimental status of lepton universality tests.

## Key findings

- Discrepancy of 3.1c3 between measurements and Standard Model predictions.
- Updated measurements suggest potential signs of new physics.
- Consistent hints across multiple experiments indicate possible lepton universality violation.

## Abstract

Tests of lepton flavour universality in charged-current $B$ decays offer an excellent opportunity to test the Standard Model, and show hints of new physics in analyses performed by the LHCb, Belle and BaBar experiments. These proceedings present the results from the LHCb collaboration on measurements of $\mathcal{R}(D^*)$ and $\mathcal{R}(J/\psi)$. It also presents the latest semileptonic tag measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ by the Belle collaboration. The latest HFLAV average shows a discrepancy of 3.1$\sigma$ between the Standard Model predictions and combined measurements of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$.