Recent $$\varvec{B}$$ 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 $$R_K$$ RK and $$R_{K^*}$$ RK∗ 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 $$R_K$$ RK and $$R_{K^*}$$ RK∗ 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 $$\mathcal{B}(B_s \rightarrow \mu ^+\mu ^-)$$ B(Bs→μ+μ-) , $$\varDelta M_{B_s}$$ ΔMBs , and angular observables in $$B \rightarrow K^{*} \mu ^+ \mu ^-$$ B→K∗μ+μ- 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