Third Family Hypercharge Model for $R_{K^{(\ast)}}$ and Aspects of the Fermion Mass Problem

Understand

We present a model to explain LHCb's recent measurements of $R_K$ and $R_{K^{\ast}}$ based on an anomaly-free, spontaneously-broken $U(1)_F$ gauge symmetry, without any fermionic fields beyond those of the Standard Model (SM).

• The model explains the hierarchical heaviness of the third family and the smallness of quark mixing.
• The $U(1)_F$ charges of the third family of SM fields and the Higgs doublet are set equal to their respective hypercharges.
• A heavy $Z^\prime$ particle with flavour-dependent couplings can modify the $[\overline{b_L} \gamma^\rho s_L][\overline{\mu_L} \gamma_\rho \mu_L]$ effective vertex in the desired way.