Interpreting hints for lepton flavor universality violation

Abstract

We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on ${R}_{K}$ and ${R}_{{K}^{*}}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of ${R}_{K}$ and ${R}_{{K}^{*}}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b\ensuremath{\rightarrow}s\ensuremath{\mu}\ensuremath{\mu}$ transition. If the hints for lepton flavor universality violation are the first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\ensuremath{\sim}100\text{ }\text{ }\mathrm{TeV}$.