On the standard model predictions for $$R_K$$ R K and $$R_{K^*}$$ R K ∗

We evaluate the impact of radiative corrections in the ratios $$Gamma [Brightarrow M mu ^+mu ^-]/Gamma [Brightarrow M mathrm{e}^+mathrm{e}^-]$$ 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 Monte Carlo codes. Our analysis reinforces the interest of these observables as clean probe of physics beyond the Standard Model.