Running coupling of the sextet composite Higgs model

TL;DR

This paper investigates the non-perturbative running coupling of an SU(3) gauge theory with sextet fermions, finding a monotonically increasing beta-function contrary to some perturbative predictions, using lattice simulations for continuum extrapolation.

Contribution

It provides the first non-perturbative lattice calculation of the running coupling in the sextet composite Higgs model, including continuum extrapolation and comparison with perturbative results.

Findings

Beta-function increases monotonically in the studied range.

Non-perturbative results differ from 3-loop and 4-loop perturbative predictions.

Continuum extrapolation confirms the robustness of the results.

Abstract

The scale-dependent renormalized coupling of SU(3) gauge theory coupled to Nf = 2 flavors of massless Dirac flavors in the sextet representation is presented in the range 0 < g^2 < 6.5. This range includes the location where the beta-function turns zero in the MSbar scheme to 3-loop and 4-loop approximations, however our non-perturbative result shows a monotonically increasing beta-function. Our lattice calclulations are carried out at several lattice spacings allowing for a controlled continuum extrapolation. We also comment on a recent similar calculation by Hasenfratz tet al.