Unitarity in Dirichlet Higgs Model

TL;DR

This paper demonstrates that a five-dimensional Universal Extra Dimension model with Dirichlet boundary conditions on a bulk Higgs field can be consistently formulated without a Higgs zero-mode, and unitarizes W+W- scattering through KK Higgs exchange.

Contribution

It introduces a novel formulation of a 5D UED model with Dirichlet boundary conditions, showing unitarization of scattering amplitudes without a Higgs zero-mode.

Findings

Unitarity is maintained up to 6.7 TeV for certain KK scales.

The scattering amplitude scales linearly with energy, indicating five-dimensional behavior.

The model aligns with electroweak data within 90% confidence level.

Abstract

We show that a five dimensional Universal Extra Dimension model, compactified on a line segment, is consistently formulated even when the gauge symmetry is broken solely by non-zero Dirichlet boundary conditions on a bulk Higgs field, without any quartic interaction. We find that the longitudinal W+W- elastic scattering amplitude, under the absence of the Higgs zero-mode, is unitarized by exchange of infinite towers of KK Higgs bosons. Resultant amplitude scales linearly with the scattering energy, exhibiting five dimensional nature. A tree-level partial-wave unitarity condition is satisfied up to 6.7 (5.7) TeV for the KK scale 430 (500) GeV, favored by the electroweak data within 90% CL.