Near-conformal dynamics in a chirally broken system

TL;DR

This study uses lattice calculations to explore how a four-light, six-heavy flavor system exhibits near-conformal behavior, revealing hyperscaling, a significant anomalous dimension, and a light scalar consistent with conformal dynamics.

Contribution

It provides the first lattice evidence of hyperscaling and a large anomalous dimension in a 4+6 flavor system near the conformal window, supporting near-conformal dynamics in composite Higgs models.

Findings

Demonstrates hyperscaling of physical quantities

Determines anomalous mass dimension y_m=1.47(5)

Finds a light 0++ scalar consistent with dilaton models

Abstract

Composite Higgs models must exhibit very different dynamics from quantum chromodynamics (QCD) regardless whether they describe the Higgs boson as a dilatonlike state or a pseudo-Nambu-Goldstone boson. Large separation of scales and large anomalous dimensions are frequently desired by phenomenological models. Mass-split systems are well-suited for composite Higgs models because they are governed by a conformal fixed point in the ultraviolet but are chirally broken in the infrared. In this work we use lattice field theory calculations with domain wall fermions to investigate a system with four light and six heavy flavors. We demonstrate how a nearby conformal fixed point affects the properties of the four light flavors that exhibit chiral symmetry breaking in the infrared. Specifically we describe hyperscaling of dimensionful physical quantities and determine the corresponding anomalous mass dimension. We obtain $y_m=1+\gamma^*= 1.47(5)$ suggesting that $N_f=10$ lies inside the conformal window. Comparing the low energy spectrum to predictions of dilaton chiral perturbation theory, we observe excellent agreement which supports the expectation that the 4+6 mass-split system exhibits near-conformal dynamics with a relatively light $0^{++}$ isosinglet scalar.