Abstract
We present a new model of composite Higgs based on a gauged SU(N) group with 4 Dirac fermions in the fundamental representation. At low energy, the model has a global symmetry SU(4)$\times$SU(4) broken to the diagonal SU(4), containing 2 Higgs doublets in the coset. We study in detail the generation of the top mass via 4-fermion interactions, and the issue of the vacuum alignment. In particular, we prove that, without loss of generality, the vacuum can always be aligned with one doublet. Under certain conditions on the top pre-Yukawas, the second doublet, together with the additional triplets, is stable and can thus play the role of Dark Matter. This model can therefore be an example of composite inert-2HDM model.
Highlights
Still ample space for extensions of the Higgs sector of the theory, and one may still expect new particles to be present at mass scales not far from the TeV scale
We present a new model of composite Higgs based on a gauged SU(N) group with 4 Dirac fermions in the fundamental representation
One way to introduce a Higgs-like boson is to extend the global symmetry of the model so that a light scalar can be left in the spectrum as a pseudo-Nambu-Goldstone boson [13, 14]
Summary
The model is based on a strongly interacting SU(N )FCD group with 4 Dirac fermions ψi in the fundamental representation. Note that the VEV in eq (2.12) is the most general one that preserves the custodial symmetry: any other choice would contribute to the ρ parameter at tree level This effect is more properly described as a misalignment of the vacuum generated by a symmetry of the broken generators. As the symmetry breaking pattern is unaltered, the pion matrix contains the same number of Goldstone bosons, which, in the new vacuum, can be parametrised as the linearly transforming matrix. As the gauge interactions (and the techni-fermion mass) are left invariant under this transformation, the Lagrangian in eq (2.15) is independent on β, once the pion fields are properly re-labeled as in eq (2.19). The transformation in eq (2.21) is generated by a U(1) symmetry which is unbroken in the EW-preserving vacuum: under such symmetry, the complex bi-doublet ΦH is charged, while the triplets and singlet are neutral. Under GP, which is compatible with a non-zero value of β, it is s and A0 to be odd, like in more traditional 2HDM models
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