Non-local Higgs actions: Tree-level electroweak constraints and high-energy unitarity

TL;DR

This paper explores non-local Higgs sectors for electroweak symmetry breaking, demonstrating unitarization of vector-boson scattering but revealing constraints from electroweak precision tests and limitations in solving the hierarchy problem.

Contribution

It introduces a gauge-invariant non-local Higgs action using a Wilson line and analyzes its implications for unitarity and electroweak constraints.

Findings

Unitarization of vector-boson scattering in non-local Higgs models.

Tree-level electroweak corrections restrict model parameters.

Unhiggs models do not solve the hierarchy problem when parameters are low-energy observables.

Abstract

We consider electroweak symmetry breaking by a certain class of non-local Higgs sectors. Extending previous studies employing the Mandelstam condition, a straight Wilson line is used to make the Higgs action gauge invariant. We show the unitarization of vector-boson scattering for a wide class of non-local actions, but find that the Wilson-line model leads to tree-level corrections to electroweak precision observables, which restrict the parameter space of the model. We also find that Unhiggs models cannot address the hierarchy problem, once the parameters are expressed in terms of low-energy observables.