TeV Scale Quark-Lepton Unification

K. S. Babu; Sumit Biswas; Shaikh Saad

Paper

TeV Scale Quark-Lepton Unification

Abstract

We propose a quark-lepton symmetric Pati-Salam (PS) model based on the gauge group

with an

-inspired particle spectrum which naturally accommodates a multi-TeV leptoquark gauge boson

. A softly broken

symmetry plays a crucial role in realizing this scenario, under which the Standard Model (SM) fermions are even, while new vector-like fermions present in the model are odd. A notable feature of this model is that the PS gauge boson

itself is

-odd, causing it to couple exclusively between SM fermions and the vector-like fermions, except in the right-handed down-quark sector, where mixing is induced by the soft breaking of

. This structure leads to helicity suppression of tree-level meson decays mediated by

, with helicity-unsuppressed contributions arising only via one-loop diagrams. We show that

can be as light as 1.1 TeV while being compatible with all flavor-violating constraints. However, mass relations among the

gauge bosons push the

mass limit up to 4.3 TeV from the stringent LHC bounds on the

mass. This comparatively low PS-breaking scale opens up promising collider opportunities for probing the leptoquark gauge boson, as well as the distinctive signature of vector-like down-type quarks carrying an unusual baryon number of

. The model can be further tested via lepton flavor-violating processes induced by the leptoquark gauge boson, such as

, and

conversion in nuclei. Neutrino masses arise in the model through dimension-seven operators at tree-level, as well as from dimension-five operators via one-loop diagrams.