Unitarity in Dirichlet Higgs Model

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.

14pages, 2 figures (v1); References added (v2); Trivial error corrected: u -> t and \cosθ-> -\cosθ, references added (v3); comments added, a reference added, version to appear in Eur. Phys. J. C (v4); Expressions matched to EPJC style, obsolete affiliation (on leave) has been removed (v5)