Implications of $b\to s$ measurements

Abstract

The recent updated angular analysis of the $B\to K^*\mu^+\mu^-$ decay by the LHCb collaboration is interpreted by performing a global fit to all relevant measurements probing the flavour-changing neutral current $b\to s\mu^+\mu^-$ transition. A significant tension with Standard Model expectations is found. A solution with new physics modifying the Wilson coefficient $C_9$ is preferred over the Standard Model by $3.7\sigma$. The tension even increases to $4.2\sigma$ including also $b\to se^+e^-$ measurements and assuming new physics to affect the muonic modes only. Other new physics benchmarks are discussed as well. The $q^2$ dependence of the shift in $C_9$ is suggested as a means to identify the origin of the tension - new physics or an unexpectedly large hadronic effect.