Neutrino masses and mixing angles in the Plan B Model

Abstract

The Plan B Model was proposed to improve the global fit quality of the Standard Model to observables involving the $b\rightarrow s \ell^+ \ell^-$ transition whilst simultaneously providing a qualitative explanation for the small magnitudes of some off-diagonal quark mixing matrix entries. The model is based on applying an additional spontaneously broken $U(1)_{3B_3-L_e-2L_μ}$ gauge symmetry to the Standard Model with family-dependent fermion charges. Right-handed neutrino fields are present and cancel gauge anomalies. We investigate the implications of the Plan B Model for neutrino masses and mixing angles. The model naturally suggests a Froggatt-Nielsen mechanism for neutrino masses and mixing hierarchies. We find that an implementation of the Froggatt-Nielsen mechanism works when additional suppression is present from a clockwork mechanism. We show how current neutrino oscillation data can be fit with order unity fundamental dimensionless couplings.