SU(6) GUT origin of the TeV-scale vectorlike particles associated with the 750 GeV diphoton resonance
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2016 American Physical Society. We consider the SU(6) grand unified theory (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 vectorlike particles having the same quantum numbers as down-type quarks and lepton doublets. These new vectorlike fermions are embedded alongside the standard model (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 vectorlike fermions arise at the TeV scale only after the residual U(1)X symmetry is broken. The vectorlike fermions do not acquire masses via breaking of the SM symmetry at the electroweak scale. The field which is responsible for the newly observed resonance belongs to the 6H representation. The dark matter arises from the SM singlet fermion residing in 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.