The Global Fits of New Physics in $b \to s $ after $R_{K^{(*)}}$ 2022 Release

Abstract

The measurement of lepton universality parameters $R_{K^{(*)}}$ was updated by LHCb in December 2022, which indicated that the well-known anomalies in flavor-changing neutral current (FCNC) processes of B meson decays have faded away. However, does this mean that all new physics possibilities related to $b\to s\ell^+\ell^-$ have been excluded? We aim to answer this question in this work. The state-of-the-art effective Hamiltonian is adopted to describe $b \to s$ transition, while BSM (beyond the Standard Model) new physics effects are encoded in Wilson coefficients (WCs). Using around 200 observables in leptonic and semileptonic decays of B mesons and bottom baryons, measured by LHCb, CMS, ATLAS, Belle, and BaBar, we perform global fits of these Wilson coefficients in four different scenarios. In particular, lepton flavors in WCs are specified in some of the working scenarios. To see the change of new physics parameters, we use both the data before and after the 2022 release of $R_{K^{(*)}}$ in two separate sets of fits. We find that in three of the four scenarios, $\Delta C_9^\mu$ still has a deviation around or more than $4\sigma$ from the Standard Model. The lepton flavor in WCs is distinguishable for $\Delta C_{9}$ at the $1\sigma$ level, but at the $2\sigma$ level all the operators are flavor identical. We demonstrate numerically that there is no chirality for muon type of scalar operator and it is kept at the $1\sigma$ level for their electron type dual ones, while chiral difference exists for $\mathcal{O}_{9}^\mu$ at least at the $2\sigma$ level. Moreover, it can be deduced that the scalar operators $\mathcal{O}_{S,P}^{(')\mu}$ become null if new physics emerges in terms of SMEFT (Standard Model Effective Field Theory) up to dimension-6.