Higgsless Electroweak Symmetry Breaking

TL;DR

This paper explores Higgsless models of electroweak symmetry breaking using extra dimensions and boundary conditions, addressing issues like unitarity, fermion masses, and precision electroweak constraints.

Contribution

It introduces a Higgsless framework with boundary conditions in extra dimensions, demonstrating how to achieve W/Z masses and delay unitarity violation without a Higgs boson.

Findings

Delayed unitarity violation via KK gauge bosons

Correct W/Z mass ratio in warped space models

Challenges with the S parameter and top quark inclusion

Abstract

We discuss the possibility of breaking the electroweak symmetry in theories with extra dimensions via boundary conditions, without a physical Higgs scalar in the spectrum. In these models the unitarity violation scale can be delayed via the exchange of massive KK gauge bosons. The correct W/Z mass ratio can be enforced in a model in warped space with a left-right symmetric gauge group in the bulk. Fermion masses can be similarly generated via boundary conditions. In the perturbative regime the S parameter is too large in the simplest model, however this can be alleviated in by changing the structure of the light fermions slightly. The major remaining issue is the inclusion of a heavy top quark without generating an unacceptably large shift in the Zbb coupling.