Dilaton Effective Field Theory

TL;DR

This paper reviews and extends dilaton effective field theory (dEFT) as a framework for describing the Higgs boson as a composite particle, including its application to lattice data and implications for model building.

Contribution

It introduces the leading and next-to-leading order formulations of dEFT, fitting lattice data and developing power-counting rules for corrections.

Findings

Successful fit of dEFT to lattice data for SU(3) with Nf=8

Development of NLO operators and estimates for their coefficients

Implications for composite-Higgs models

Abstract

We review and extend recent studies of dilaton effective field theory (dEFT) which provide a framework for the description of the Higgs boson as a composite structure. We first describe the dEFT as applied to lattice data for a class of gauge theories with near-conformal infrared behavior. It includes the dilaton associated with the spontaneous breaking of (approximate) scale invariance, and a set of pseudo-Nambu-Goldstone bosons (pNGBs) associated with the spontaneous breaking of an (approximate) internal global symmetry. The theory contains two small symmetry-breaking parameters. We display the leading-order (LO) Lagrangian, and review its fit to lattice data for the $SU(3)$ gauge theory with $N_f = 8$ Dirac fermions in the fundamental representation. We then develop power-counting rules to identify the corrections emerging at next-to-leading order (NLO) in the dEFT action. We list the NLO operators that appear and provide estimates for the coefficients. We comment on implications for composite-Higgs model building.