# Impacts of radiative corrections on measurements of lepton flavour universality in $B \to D \ell \nu_{\ell}$ decays

## TL;DR

This paper investigates how radiative corrections, including soft-photon effects and Coulomb interactions, influence measurements of lepton flavour universality ratios in B meson decays, highlighting potential biases in experimental results.

## Contribution

It compares recent theoretical calculations of radiative corrections with PHOTOS simulations and assesses their impact on lepton universality measurements in B decays.

## Key findings

- Soft-photon corrections can cause up to 7% bias in $ ext{R}(D)$ measurements.
- Coulomb interactions, not included in PHOTOS, also affect the ratios.
- High-energy photon emission introduces measurable biases in LHCb-like environments.

## Abstract

Radiative corrections to $B \to D \ell \nu_{\ell}$ decays can have an impact on predictions and measurements of the lepton universality ratios $\mathcal{R}(D^+)$ and $\mathcal{R}(D^0)$. These proceedings summarise a study on the comparison between recent calculations of soft-photon corrections on these ratios and the corrections simulated by the PHOTOS package. Also the impact of Coulomb interactions, not simulated in PHOTOS, is discussed. Using pseudo-experiments, the effect of high-energy photon emission is studied in an LHCb-like environment, showing a bias of up to 7\% on measurements of $\mathcal{R}(D)$.