On the Standard Model predictions for $R_K$ and $R_{K^*}$

TL;DR

This paper assesses radiative corrections in B-meson decay ratios involving muons and electrons, confirming their small impact and reinforcing their role as clean probes for new physics beyond the Standard Model.

Contribution

The study quantifies radiative corrections in $R_K$ and $R_{K^*}$ ratios, showing they are minimal and well-managed by current Monte Carlo tools, supporting their use in new physics searches.

Findings

Radiative corrections do not exceed a few percent.

Existing Monte Carlo codes effectively account for these corrections.

Ratios remain clean probes for physics beyond the Standard Model.

Abstract

We evaluate the impact of radiative corrections in the ratios $\Gamma[B\to M \mu^+\mu^-]/\Gamma[B\to M e^+e^-]$ when the meson $M$ is a $K$ or a $K^*$. Employing the cuts on $m^2_{\ell\ell}$ and the reconstructed $B$-meson mass presently applied by the LHCb Collaboration, such corrections do not exceed a few $\%$. Moreover, their effect is well described (and corrected for) by existing Montecarlo codes. Our analysis reinforces the interest of these observables as clean probe of physics beyond the Standard Model.