Third Family Quark-Lepton Unification at the TeV Scale

TL;DR

This paper proposes a TeV-scale quark-lepton unification model based on an $SU(4)$ gauge symmetry, predicting observable effects like leptoquark production and deviations in neutrino mixing, while addressing recent B-meson decay anomalies.

Contribution

It introduces a novel $SU(4)$-based unification model at the TeV scale that naturally explains CKM mixing and predicts testable phenomena such as leptoquarks and unitarity violations.

Findings

Predicts sizeable violation of PMNS unitarity

Forecasts leptoquark production at the LHC

Addresses B-meson decay anomalies

Abstract

We construct a model of quark-lepton unification at the TeV scale based on an $SU(4)$ gauge symmetry, while still having acceptable neutrino masses and enough suppression in flavor changing neutral currents. An approximate $U(2)$ flavor symmetry is an artifact of family-dependent gauge charges leading to a natural realization of the CKM mixing matrix. The model predicts sizeable violation of PMNS unitarity as well as a gauge vector leptoquark $U_1^\mu = ({\bf 3}, {\bf 1}, 2/3)$ which can be produced at the LHC -- both effects within the reach of future measurements. In addition, recently reported experimental anomalies in semi-leptonic $B$-meson decays, both in charged $b \to c \tau \nu$ and neutral $b \to s \mu \mu$ currents, can be accommodated.