Can the nearly conformal sextet gauge model hide the Higgs impostor?

TL;DR

This study uses lattice simulations to investigate whether the sextet gauge model exhibits chiral symmetry breaking or conformal behavior, suggesting it could produce a light scalar state resembling the Higgs boson.

Contribution

The paper provides new lattice simulation results indicating the sextet model is near the conformal window, supporting a composite Higgs mechanism with a potential light scalar as a pseudo-Goldstone dilaton.

Findings

Chiral condensate and mass spectrum are consistent with chiral symmetry breaking.

Spectral properties do not match conformal scaling near the critical surface.

The model is close to the conformal window with a small but non-zero beta function.

Abstract

New results are reported from large scale lattice simulations of a frequently discussed strongly interacting gauge theory with a fermion flavor doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. We find that the chiral condensate and the mass spectrum of the sextet model are consistent with chiral symmetry breaking in the limit of vanishing fermion mass. In contrast, sextet fermion mass deformations of spectral properties are not consistent with leading conformal scaling behavior near the critical surface of a conformal theory. A recent paper could not resolve the conformal fixed point of the gauge coupling from the slowly walking scenario of a very small nearly vanishing \beta-function (DeGrand:2012yq). It is argued that overall consistency with our new results is resolved if the sextet model is close to the conformal window, staying outside with a very small non-vanishing \beta-function. The model would exhibit then the simplest composite Higgs mechanism leaving open the possibility of a light scalar state with quantum numbers of the Higgs impostor. It would emerge as the pseudo-Goldstone dilaton state from spontaneous symmetry breaking of scale invariance. We will argue that even without association with the dilaton, the scalar Higgs-like state can be light very close to the conformal window. A new Higgs project of sextet lattice simulations is outlined to resolve these important questions.