Neutrino mixing and R_K anomaly in U(1)_X models: a bottom-up approach

We identify a class of U(1)_X models which can explain the R_K anomaly and the neutrino mixing pattern, by using a bottom-up approach. The different X-charges of lepton generations account for the lepton universality violation required to explain R_K. In addition to the three right-handed neutrinos needed for the Type-I seesaw mechanism, these minimal models only introduce an additional doublet Higgs and a singlet scalar. While the former helps in reproducing the quark mixing structure, the latter gives masses to neutrinos and the new gauge boson Z^′. Our bottom-up approach determines the X-charges of all particles using theoretical consistency and experimental constraints. We find the parameter space allowed by the constraints from neutral meson mixing, rare b→s decays and direct collider searches for Z^′. Such a Z^′ may be observable at the ongoing run of the Large Hadron Collider with a few hundred fb⁻¹ of integrated luminosity.