Ideal walking dynamics via a gauged NJL model

Abstract

According to the Ideal Walking Technicolor paradigm large mass anomalous dimensions arise in gauged Nambu-Jona-Lasinio (NJL) models when the four-fermion coupling is sufficiently strong to induce spontaneous symmetry breaking in an otherwise conformal gauge theory. We therefore study the SU (2) gauged NJL model with two adjoint fermions using lattice simulations. The model is in an infrared conformal phase at small NJL coupling while it displays a chirally broken phase at large NJL couplings. In the infrared conformal phase we find that the mass anomalous dimension varies with the NJL coupling reaching γm ∼ 1 close to the chiral symmetry breaking transition, de facto making the present model the first explicit realization of the Ideal Walking scenario.

Vacuum alignment in a composite 2HDM

“…The object we defined above, which transforms linearly under SU (6), can be used to define the chiral Lagrangian…”

“…In the latter case, the linear mixing with the SM fermions would arise at dimension larger than 9, implying a stronger suppression. 6 By increasing the number of fermions, before losing asymptotic freedom, the model will enter the conformal window [65,66], thus losing the formation of a condensate and mass gap. This further limits the Model 2 to N c = 2 [67] for the minimal fermion content in Table II.…”

“…We finally remark that an underlying theory similar to the one we are interested in has been used in Refs [40,41] to construct a Little Higgs model, where the light Higgs also arises as a pNGB from the SU(6)/Sp (6) coset. The main difference between the two approaches is that in Little Higgs models the gauged subgroup is more extended than the electroweak (EW) one, and the additional gauge generators are assumed to be broken at the condensation scale.…”

“…A. Preliminaries: SU(6) → Sp (6) The unbroken group Sp (6), of rank 3, contains 3 commuting SU(2) subgroups: it is thus natural to try to identify them with the EW sector of the SM, i.e. the gauged SU(2) L and the partly-gauged SU(2) R .…”

“…A composite Higgs boson can, thus, be identified with any one of the 3 bi-doublets. To classify the various possibilities, it is useful to list the quantum number assignments of a fundamental 6 of SU (6), ψ, that will correspond to the techni-fermions in the underlying gauge-fermion model. Each sextet ψ can be decomposed into 3 doublets ψ i , i = 1, 2, 3, each one transforming under a different global SU(2) i .…”