Flavoured $B-L$ Local Symmetry and Anomalous Rare $B$ Decays

We consider a flavoured B−L gauge symmetry under which only the third generation fermions are charged. Such a symmetry can survive at low energies ( ∼TeV ) while still allowing for two superheavy right-handed neutrinos, consistent with neutrino masses via see-saw and leptogenesis. We describe a mechanism for generating Yukawa couplings in this model and also discuss the low-energy phenomenology. Interestingly, the new gauge boson could explain the recent hints of lepton universality violation at LHCb, with a gauge coupling that remains perturbative up to the Planck scale. Finally, we discuss more general U(1) symmetries and show that there exist only two classes of vectorial U(1) that are both consistent with leptogenesis and remain phenomenologically viable at low-energies.