Models of Walking Technicolor on the Lattice

TL;DR

This paper investigates whether a specific QCD-like theory with 2 colour-sextet quarks exhibits walking behavior or conformal properties by analyzing the running of the lattice coupling at finite temperature.

Contribution

It provides lattice simulation results indicating the coupling runs slower than asymptotic freedom predicts, suggesting walking behavior rather than conformality.

Findings

Coupling runs slower than predicted by 2-loop perturbation theory.

Results suggest the theory may exhibit walking behavior.

Study extends to lattices with up to 12 temporal extents.

Abstract

We study QCD with 2 colour-sextet quarks as a walking-Technicolor candidate. As such it provides a description of the Higgs sector of the standard model, in which the Higgs field is replaced by the Goldstone `pions' of this QCD-like theory, and the Higgs itself is the $\sigma$. Such a theory will need to be extended if it is to also give masses to the quarks and leptons. What we are attempting to determine is whether it is indeed QCD-like and hence walking, or if it has an infrared fixed point making it a conformal field theory. We do this by simulating its lattice version at finite temperature and observing the running of the bare (lattice) coupling at the chiral transition, as the lattice spacing is varied, and comparing this running with that predicted by 2-loop perturbation theory. Our results on lattices with temporal extents ($N_t$) up to 12 indicate that the coupling runs, but not as fast as asymptotic freedom predicts. We discuss our program for studying the zero-temperature phenomenology of this theory.