Gauge coupling unification in a minimal non-supersymmetric $E_6$ GUT

TL;DR

This paper proposes a minimal non-supersymmetric $E_6$ GUT model that achieves gauge unification with TeV-scale vector-like fermions and scalar leptoquarks, explaining flavor anomalies and neutrino masses while being consistent with proton decay limits.

Contribution

It introduces a novel minimal $E_6$ GUT framework with direct symmetry breaking, minimal threshold uncertainties, and explanations for flavor anomalies and neutrino masses.

Findings

Successful gauge unification without intermediate symmetry

Compatibility with proton decay constraints

Potential explanation for flavor anomalies and muon g-2

Abstract

We consider a minimal renormalizable non-supersymmetric $E_6$ Grand Unified Theory using fundamental representation $27$ for fermions and scalars. The scalar with adjoint representation ${78}$ is also taken for direct breaking of $E_{6}$ to SM. The proposed model, guided by TeV-scale vector-like fermions and scalar leptoquark offer successful gauge unification even in the absence of any intermediate symmetry. Embedded with threshold corrections, it is shown to be compatible with the present experimental limit on proton decay lifetime. The unique feature of the model shows that, the GUT threshold corrections to the unification mass, is controlled by superheavy gauge bosons only, thereby minimising the uncertainty of the GUT predictions. The scalar leptoquark and vector-like fermions residing in $27$ representation can explain flavor physics anomalies like $R_{D^{(\ast)}}$ as reported by the LHCb collaboration and the muon anomalous magnetic moment reported by the recent muon $g-2$ experiment at Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level via exchange of $W$ and $Z$ gauge bosons through MRIS mechanism.