Status of the $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ anomaly after Moriond 2017

Abstract

Motivated by recent results by the ATLAS and CMS collaborations on the angular distribution of the $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ decay, we perform a state-of-the-art analysis of rare $B$ meson decays based on the $b\to s\mu \mu$ transition. Using standard estimates of hadronic uncertainties, we confirm the presence of a sizable 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.

Comments: 20 pages, 8 figures, 3 tables. v3: numerics updated using v2 of arXiv:1606.04731. Conclusions unchanged. Matches published version. Example script available at https://github.com/DavidMStraub/paper-bkstarmumu-anss