Recent $\boldsymbol{B}$ Physics Anomalies - a First Hint for Compositeness?

Abstract

We scrutinize the recently further strengthened hints for new physics in semileptonic $B$-meson decays, focusing on the 'clean' ratios of branching fractions $R_K$ and $R_{K^\ast}$ and examining to which pattern of new effects they point to. We explore in particular the hardly considered, yet fully viable, option of new physics in the right-handed electron sector and demonstrate how a recently proposed framework of leptons in composite Higgs setups naturally solves both the $R_K$ and $R_{K^\ast}$ anomalies via a peculiar structure of new physics effects, predicted by minimality of the model and the scale of neutrino masses. Finally, we also take into account further observables, such as ${\cal B}(B_s \to \mu^+\mu^-)$, $\Delta M_{B_s}$, and angular observables in $B \to K^{\ast} \mu^+ \mu^-$ decays, to arrive at a comprehensive picture of the model concerning (semileptonic) $B$ decays. We conclude that -- since it is in good agreement with the experimental situation in flavor physics and also allows to avoid ultra-light top partners -- the model furnishes a very promising scenarios of Higgs compositeness in the light of LHC data.