Flavour non-universal Pati-Salam unification and neutrino masses

TL;DR

This paper proposes a three-site, flavour non-universal Pati-Salam model that explains B anomalies, fermion mass hierarchies, and neutrino masses, predicting observable PMNS unitarity violation and a natural extra-dimensional interpretation.

Contribution

It introduces a novel three-site Pati-Salam framework with inverse seesaw for neutrinos, linking flavour anomalies, mass hierarchies, and extra-dimensional theories.

Findings

Explains B anomalies through flavour non-universal gauge interactions.

Predicts PMNS unitarity violation near current experimental bounds.

Provides a natural 5D interpretation with hierarchical VEV ratios.

Abstract

The B anomalies, by their distinctive flavour structure i.e. $U(2)^5$, bring a new piece to the long-standing flavour puzzle. The three-site flavour non-universal Pati-Salam (PS) model, which unifies quarks and leptons, provides through the ratios of vacuum expectation values (VEV) acquired at different scales, a combined explanation of the charged and neutral current B anomalies as well as of the mass hierarchies of the Standard Model (SM). The mixings, in new, flavour non-universal, gauge interactions, as well as in the Yukawa couplings, are obtained through suppressed nearest-neighbour interactions. In this three-site model context, the inverse seesaw mechanism is realised, with the minimal addition of three fermion singlets $S_L^{(i)}$ and where $U(1)_F$ fermion number is broken dynamically via new singlet scalars $\Phi_i$, yielding an anarchic light neutrino mass matrix in consistency with data, despite the $U(2)^5$ flavour symmetry observed in the Yukawa matrices. A prediction of this model is Pontecorvo-Maki-Nakagawa-Sakata (PMNS) unitarity violation with a $33$ entry close to experimental bounds. The full model finds a natural 5D interpretation with three (almost equidistant) defects in a warped extra dimension, where the exponential hierarchies in VEV ratios of the 4D Lagrangian arise from O(1) differences in the 5D field bulk masses. This proceeding is based on arXiv:2012.10492.