Bulk Higgs with 4D Gauge Interactions

TL;DR

This paper proposes a model with a bulk Higgs field in a 5D setup where gauge invariance is preserved, leading to a Higgs that behaves as a 4D field and affects electroweak parameters.

Contribution

It introduces a consistent way to incorporate a bulk Higgs in 4D gauge theories, modifying the Higgs propagator and electroweak mixing without losing gauge invariance.

Findings

Higgs behaves as a 4D field despite being in the bulk

Photon remains massless in the model

Higgs vacuum induces mixing affecting the -parameter

Abstract

We consider a model with an extra compact dimension in which the Higgs is a bulk field while all other Standard Model fields are confined on a brane. We find that four-dimensional gauge invariance can still be achieved by appropriate modification of the brane action. This changes accordingly the Higgs propagator so that, the Higgs, in all its interactions with Standard Model fields, behaves as an ordinary 4D field, although it has a bulk kinetic term and bulk self-interactions. In addition, it cannot propagate from the brane to the bulk and, thus, no charge can escape into the bulk but it remains confined on the brane. Moreover, the photon remains massless, while the dependence of the Higgs vacuum on the extra dimension induces a mixing between the graviphoton and the Z-boson. This results in a modification of the sensitive \rho-parameter.