# Status of the $B\to K^*\mu^+\mu^-$ anomaly after Moriond 2017

## TL;DR

This paper analyzes recent anomalies in $B o K^* o \,\mu^+\mu^-$ decays, confirming a significant deviation from Standard Model predictions and proposing new physics as a possible explanation, with implications for lepton flavor universality.

## Contribution

It provides a comprehensive analysis of the $B o K^* \,\mu^+\mu^-$ anomaly post-Moriond 2017, supporting new physics explanations involving four-fermion interactions.

## Key findings

- Confirmed sizable discrepancy between data and SM predictions.
- No evidence for $q^2$ or helicity dependence of the anomaly.
- Predicted observables sensitive to lepton flavor universality violation.

## Abstract

Motivated by recent results by the ATLAS and CMS collaborations on the angular distribution of the $B \to K^* \mu^+\mu^-$ 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.