E6 GUT and Baryon Asymmetry Generation in the E6CHM

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.

Generation of baryon asymmetry in the E6CHM

The strongly interacting sector in theE6inspired composite Higgs model (E6CHM) with baryon number violation possesses an SU(6) ×U(1)Lglobal symmetry. In the weakly-coupled sector of this model theU(1)Lsymmetry associated with lepton number conservation is broken down to aZL2discrete symmetry, which stabilizes the proton. Near the scalef≳ 10 TeV the SU(6) symmetry is broken down to its SU(5) subgroup, giving rise to a set of pseudo- Nambu-Goldstone bosons (pNGBs) that involves the SM-like Higgs doublet, a scalar coloured triplet and a SM singlet boson. Becausefis so high, all baryon number violating operators are sufficiently strongly suppressed. Nevertheless, in this variant of the E6CHM the observed matter-antimatter asymmetry can be induced if CP is violated. The pNGB scalar coloured triplet plays a key role in this process and leads to a distinct signature that may be detected at the LHC in the near future.