Implication of family non-universal $Z'$ model to rare exclusive $b \to s(l\bar l,\nu\bar\nu)$ transitions

Abstract

We have investigated $B \to (K,K^*)(l\bar l,\nu\bar\nu)$ decay channels and predicted some form factor dependent observables (e.g. branching ratio, forward-backward asymmetry and lepton polarization asymmetry) considering new physics contribution from non-universal $Z'$ model. We have found that there is appreciable difference between the standard model and $Z'$ model predictions. Recently, the lepton flavour non-universality parameters $R_K$ and $R_{K^*}$ have been measured by the LHCb collaboration and are found to be different from their standard model predictions. These deviations provide the hint of flavor non-universality in lepton sector and motivate our research to look for new physics beyond the standard model. The $R_K$ and $R_{K^*}$ anomalies may be due to new physics in either electron or muon sector or both. In our work, we have shown that the experimental results of $R_K$ and $R_{K^*}$ could be achieved in non-universal $Z'$ model considering the new physics couplings to muon sector only.