E₆ inspired composite Higgs model

Abstract

We consider a composite Higgs model embedded into a grand unified theory (GUT) based on the E₆ gauge group. The phenomenological viability of this E6inspired composite Higgs model (E₆CHM) implies that standard model (SM) elementary fermions with different baryon or lepton number should stem from 27 different representations of E₆. We present a six-dimensional orbifold GUT model in which the E₆ gauge symmetry is broken to the SM gauge group so that the appropriate splitting of the bulk 27-plets takes place. In this model the strongly coupled sector is localized on one of the branes and possesses an SU(6) global symmetry that contains the SU(3)C×SU(2)W×U(1)Y subgroup. In this case the approximate gauge coupling unification can be attained if the right-handed top quark is a composite state and the elementary sector involves extra exotic matter beyond the SM which ensures anomaly cancellation. The breakdown of the approximate SU(6) symmetry at low energies in this model results in a set of the pseudo-Nambu-Goldstone states which include a Higgs doublet and scalar color triplet. We discuss the generation of the masses of the SM fermions in the E₆CHM. The presence of the TeV scale vectorlike exotic quarks and scalar color triplet may provide spectacular new physics signals that can be observed at the LHC.