Dirichlet Higgs in extra-dimension, consistent with electroweak data

TL;DR

This paper introduces a five-dimensional Higgs model with Dirichlet boundary conditions that breaks electroweak symmetry without a potential, predicting distinctive Yukawa coupling deviations consistent with electroweak data.

Contribution

It presents a novel 5D Higgs model with boundary conditions inducing symmetry breaking, avoiding a Higgs potential, and analyzes its phenomenological implications.

Findings

Maximal top Yukawa deviation for brane-localized fermions.

Small Yukawa deviation (~0.9) for bulk fermions.

Model consistent with electroweak precision data for KK masses 430-500 GeV.

Abstract

We propose a simple five-dimensional extension of the Standard Model (SM) without any Higgs potential nor any extra fields. A Higgs doublet lives in the bulk of a flat line segment and its boundary condition is Dirichlet at the ends of the line, which causes the electroweak symmetry breaking without Higgs potential. The vacuum expectation value of the Higgs is induced from the Dirichlet boundary condition which is generally allowed in higher dimensional theories. The lightest physical Higgs has non-flat profile in the extra dimension even though the vacuum expectation value is flat. As a consequence, we predict a maximal top Yukawa deviation (no coupling between top and Higgs) for the Brane-Localized Fermion and a small deviation, a multiplication of 2\sqrt{2}/\pi\simeq0.9 to the Yukawa coupling, for the Bulk Fermion. The latter is consistent with the electroweak precision data within 90% CL for 430GeV\lesssim m_{KK}\lesssim 500GeV.