$b\to s\ell \ell$ Global Fits after $R_{K_S}$ and $R_{K^{\ast +}}$

Abstract

We present an up-to-date complete model-independent global fit to $b\to s{\ell }^{+}{\ell }^{-}$ observables that confirms patterns of New Physics able to explain the data. We include the recent LHCb measurements of $R_K$, $R_{K_S}$, $R_{K^{\ast +}}$, $B_s\to \varphi {\mu }^{+}{\mu }^{-}$ and $B_s\to \mu \mu$ in our analysis, which now includes 254 observables. This updates our previous analyses and strengthens their two main outcomes. First, the presence of right-handed couplings encoded in the Wilson coefficients ${\mathcal{C}}_{9^{\prime }\mu }$ and ${\mathcal{C}}_{10^{\prime }\mu }$ remains a viable possibility. Second, a lepton flavour universality violating (LFUV) left-handed lepton coupling (${\mathcal{C}}_{9\mu }^{\mathrm{V}}=-{\mathcal{C}}_{10\mu }^{\mathrm{V}}$), often preferred from the model building point of view, accommodates the data better if lepton-flavour universal New Physics is allowed, in particular in ${\mathcal{C}}_9^{\mathrm{U}}$. We observe that the LFUV observable $Q_5$ offers a very interesting possibility to separate both types of scenarios.

Comments: Version accepted for publication in EPJC, extended to include SM predictions for all observables in the fits and additional references