Dirichlet Higgs in extra-dimension, consistent with electroweak data

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.