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Gauge-Assisted Technicolor?

Maxim Perelstein

TL;DR

This work probes electroweak symmetry breaking without a fundamental Higgs by extending the gauge sector with extra SU(2) and U(1) factors, including deconstructed 5D Higgsless scenarios. Using a four-dimensional non-linear sigma model and the Barbieri–Pomarol–Rattazzi–Strumia framework, it separates mixing effects of heavy gauge states from genuine short-distance physics and expresses their impact on precision observables through the oblique parameter $\hat{S}$. The analysis finds that extended gauge structures do not suppress the sensitivity of low-energy $W/Z$ observables to TeV-scale strong dynamics; in particular, QCD-like technicolor remains strongly disfavored unless unnatural cancellations occur between contributions, which cannot occur for QCD-like UV completions. Consequently, the explored gauge extensions do not salvage Higgsless/technicolor-like EWSB, and the results constrain the viability of deconstructed extra-dimensional models as alternatives to a light Higgs. The study also clarifies how deconstruction maps to 5D theories and highlights the persistent challenges in achieving viable EWSB without a light scalar.

Abstract

It is well known that technicolor models in which the electroweak symmetry is broken by QCD-like strong dynamics at the TeV scale generally predict unacceptably large corrections to low-energy observables. We investigate the models of electroweak symmetry breaking by strong dynamics in which the gauge symmetry is extended to include an arbitrary number of additional SU(2) and U(1) factors. This class of models includes the deconstructed version of the recently proposed five-dimensional "Higgsless" scenario. We conclude that the additional structure present in these theories does not suppress the effects of strongly coupled short-distance physics on the precision electroweak observables. In particular, the possibility that the symmetry breaking is due to QCD-like dynamics is still strongly disfavored by data.

Gauge-Assisted Technicolor?

TL;DR

This work probes electroweak symmetry breaking without a fundamental Higgs by extending the gauge sector with extra SU(2) and U(1) factors, including deconstructed 5D Higgsless scenarios. Using a four-dimensional non-linear sigma model and the Barbieri–Pomarol–Rattazzi–Strumia framework, it separates mixing effects of heavy gauge states from genuine short-distance physics and expresses their impact on precision observables through the oblique parameter . The analysis finds that extended gauge structures do not suppress the sensitivity of low-energy observables to TeV-scale strong dynamics; in particular, QCD-like technicolor remains strongly disfavored unless unnatural cancellations occur between contributions, which cannot occur for QCD-like UV completions. Consequently, the explored gauge extensions do not salvage Higgsless/technicolor-like EWSB, and the results constrain the viability of deconstructed extra-dimensional models as alternatives to a light Higgs. The study also clarifies how deconstruction maps to 5D theories and highlights the persistent challenges in achieving viable EWSB without a light scalar.

Abstract

It is well known that technicolor models in which the electroweak symmetry is broken by QCD-like strong dynamics at the TeV scale generally predict unacceptably large corrections to low-energy observables. We investigate the models of electroweak symmetry breaking by strong dynamics in which the gauge symmetry is extended to include an arbitrary number of additional SU(2) and U(1) factors. This class of models includes the deconstructed version of the recently proposed five-dimensional "Higgsless" scenario. We conclude that the additional structure present in these theories does not suppress the effects of strongly coupled short-distance physics on the precision electroweak observables. In particular, the possibility that the symmetry breaking is due to QCD-like dynamics is still strongly disfavored by data.

Paper Structure

This paper contains 6 sections, 22 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Electroweak Symmetry Breaking by Strong Interactions
  3. The Minimal Model
  4. Precision Electroweak Constraints
  5. Technicolor Models
  6. A Prototype Model with an Extended Gauge Sector: $SU(2)\times SU(2)\times U(1)$

Figures (1)

  • Figure 1: The diagram representing the symmetry breaking pattern of the model studied in Section 3. Each circle indicates a global $SU(2)$ symmetry; the gauged subgroup is indicated inside the circle. The lines connecting the circles represent the bifundamental scalar fields $\Sigma_{0,1}$ whose vacuum expectation values break the symmetries.