An SU(6) GUT Origin of the TeV-Scale Vector-like Particles Associated with the 750 GeV Diphoton Resonance

TL;DR

This paper proposes an $SU(6)$ GUT model explaining the 750 GeV diphoton resonance with new vector-like particles at the TeV scale, unifying gauge couplings, and predicting additional LHC-accessible signals.

Contribution

It introduces a minimal anomaly-free $SU(6)$ GUT framework linking the diphoton excess to TeV-scale vector-like fermions and dark matter, with explicit gauge unification and neutrino mass mechanisms.

Findings

Gauge coupling unification demonstrated.

Predictions for additional LHC signals.

Dark matter as a Majorana fermion in the model.

Abstract

We consider the $SU(6)$ GUT model as an explanation for the diphoton final state excess, where the masses of all associated particles are linked with a new symmetry breaking scale. In this model, the diphoton final states arise due to loops involving three pairs of new vector-like particles having the same quantum numbers as down-type quarks and lepton doublets. These new vector-like fermions are embedded alongside the SM fermions into minimal anomaly-free representations of the $SU(6)$ gauge symmetry. The $SU(6)$ symmetry is broken to the Standard Model times $U(1)_X$ at the GUT scale, and masses for the vector-like fermions arise at the TeV scale only after the residual $U(1)_X$ symmetry is broken. The vector-like fermions do not acquire masses via breaking of the SM symmetry at the EW scale. The field which is responsible for the newly observed resonance belongs to the $\bar{6}_H$ representation. The dark matter arises from the SM singlet fermion residing in $\bar{6}$ and is of Majorana type. We explicitly demonstrate gauge coupling unification in this model, and also discuss the origin of neutrino masses. In addition to the diphoton final states, we make distinctive predictions for other final states which are likewise accessible to the ongoing LHC experimental effort.