Lattice-friendly gauge completion of a composite Higgs with top partners

Abstract

We give an explicit example of a composite Higgs model with a pseudo-Nambu-Goldstone Higgs in which the top Yukawa coupling is generated via the partial compositeness mechanism. This mechanism requires composite top partners which are relatively light compared to the typical mass scale of the strongly coupled theory. While most studies of the phenomenology of such models have focused on a bottom-up approach with a minimal effective theory, a top-down approach suggests that the theory should contain a limit in which an unbroken global chiral symmetry protects the mass of the top partners, and the spectrum of the partners satisfies 't Hooft matching conditions. We find that the relatively light fermions and pseudo-Goldstone bosons fall into complete multiplets of a large approximate global symmetry, and that the spectrum of particles lighter than a few TeV is non-minimal. Our example illustrates the likely features of a such a composite Higgs theory and also serves as an example of a non-chiral theory with a possible solution to the 't Hooft matching conditions. We find in this example that for some low-energy parameters in the effective theory the top partners can decay into high-multiplicity final states, which could be difficult for the Large Hadron Collider (LHC) to constrain. This may potentially allow for the top partners to be lighter than those in more minimal models.

Sp (4) gauge theories on the lattice: Nf = 2 dynamical fundamental fermions

“…Particular attention has been devoted to models and dynamical theories characterised by the SU (4)/Sp(4) coset (see for instance Refs. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59]). The low-energy EFT Lagrangian contains, in this case, five scalar fields, that describe the long-distance dynamics of the five pNGBs.…”

Strong dynamics with matter in multiple representations: $$\mathrm {SU}(4)$$ gauge theory with fundamental and sextet fermions

“…In this respect, a novel and interesting proposal for a different strongly coupled New Physics model has been recently put forward in Ref. [37]. Like in the model that we considered here [16], the idea underlying the construction of this model is that the contributions to the Higgs boson mass from its Yukawa coupling to the top quark can be partially compensated for by the presence of sufficiently light top partners.…”

“…[16], the model discussed in Ref. [37] is characterized by local invari-ance under a symplectic, rather than a special unitary, group.…”

“…More specifically, the model described in Ref. [37] is based on the SU(4)/Sp(4) symmetry-breaking scheme [10,38] and its ultraviolet completion is a vector gauge theory with local internal invariance under the Sp(6) group. In addition to the gauge bosons, the field content of the theory includes ten fermions in the fundamental representation, and one in the adjoint representation of the gauge group.…”

“…As discussed in Ref. [37], this model is expected to present a rich low-energy phenomenology, which could include top-quark partners, scalar particles, and color-charged fermions. These features make it an interesting target for non-perturbative lattice calculations -a research program that could be a natural generalization of the present work.…”