Abstract
Grand unified theories (GUTs) may result in the E6-inspired composite Higgs model (E6CHM) at low energies, almost stabilizing the electroweak scale. We consider an orbifold GUT in 6 dimensions in which the E6-gauge group is broken to the gauge symmetry of the standard model (SM) while different multiplets of the SM fermions come from different 27-plets. The strongly coupled sector of the E6CHM is confined on the brane where E6 is broken down to its SU(6) subgroup. Near the scale of f≳5TeV, this approximate SU(6) symmetry is expected to be further broken down to its SU(5) subgroup, which contains the SM-gauge group. Such a breakdown leads to a set of pseudo-Nambu–Goldstone bosons (pNGBs) that includes an SM-like Higgs doublet. The approximate gauge coupling unification in the E6CHM takes place at high energies when the right-handed top quark is a composite fermion. To ensure anomaly cancellation, the weakly coupled sector of this model contains extra exotic matter beyond the SM. We discuss the mechanism of the generation of matter–antimatter asymmetry within the variant of the E6CHM in which the baryon number and CP invariance are violated.
Highlights
It is well known that the standard model (SM) of elementary particles, which involves all known fundamental bosons and fermions, describes rather precisely the major part of all experimental data
At low energies E f the baryon number violating processes are suppressed within the E6-inspired composite Higgs model (E6CHM), a sizeable baryon number asymmetry may still be generated via the out-of-equilibrium decays of N1 if N1 has a mass which is substantially lower than the masses of all other composite and exotic fermions
The E6CHM can originate from the SUSY grand unified theories (GUTs) based on the E6 × G0-gauge symmetry
Summary
It is well known that the standard model (SM) of elementary particles, which involves all known fundamental bosons and fermions, describes rather precisely the major part of all experimental data. Due to the mixing between the elementary states and their composite partners, the interactions in the strongly coupled sector may induce the dimension-5 operators of the form i j HH/ f , which give rise to overly large Majorana neutrino masses, as well as a set of baryon number-violating operators. All these operators are suppressed by the small fractions of compositeness of the SM fermions and by the relatively large scale f. In the E6CHM, the lepton number is preserved to a very good approximation, κij are expected to be very small, giving rise to tiny masses of the left-handed neutrinos
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