Status of the $$B\rightarrow K^*\mu ^+\mu ^-$$ B → K ∗ μ + μ - anomaly after Moriond 2017

Motivated by recent results by the ATLAS and CMS collaborations on the angular distribution of the $$B \rightarrow K^* \mu ^+\mu ^-$$ decay, we perform a state-of-the-art analysis of rare B meson decays based on the $$b \rightarrow s \mu \mu $$ transition. Using standard estimates of hadronic uncertainties, we confirm the presence of a sizeable discrepancy between data and SM predictions. We do not find evidence for a $$q^2$$ or helicity dependence of the discrepancy. The data can be consistently described by new physics in the form of a four-fermion contact interaction $$(\bar{s} \gamma _\alpha P_L b)(\bar{\mu }\gamma ^\alpha \mu )$$ . Assuming that the new physics affects decays with muons but not with electrons, we make predictions for a variety of theoretically clean observables sensitive to violation of lepton flavour universality.