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

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 $R_K$, $R_{K_S}$, $R_{K^{*+}}$, $B_s \to \phi\mu^+\mu^-$ 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 $\mathcal{C}_{9'\mu}$ and $\mathcal{C}_{10'\mu}$ remains a viable possibility. Second, a lepton flavour universality violating (LFUV) left-handed lepton coupling ($\mathcal{C}_{9\mu}^{\rm V}=-\mathcal{C}_{10\mu}^{\rm V}$), often preferred from the model building point of view, accommodates the data better if lepton-flavour universal New Physics is allowed, in particular in $\mathcal{C}_{9}^{\rm U}$. We observe that the LFUV observable $Q_5$ offers a very interesting possibility to separate both types of scenarios.