Flavourful Z ′ models for R K ∗ R_K( )

We show how any flavour conserving Z ′ model can be made flavour violating and non-universal by introducing mass mixing of quarks and leptons with a fourth family of vector-like fermions with non-universal Z ′ couplings. After developing a general formalism, we focus on two concrete examples, namely a fermiophobic model, and an SO(10) GUT model, and show how they can account for the anomalous B decay ratios R K and RK_ . A similar analysis could be performed for B − L models, E 6 models, composite models, and so on.