Unification of Higgs and gauge fields in five dimensions

We construct realistic theories in which the Higgs fields arise from extra-dimensional components of higher-dimensional gauge fields. In particular, we present a minimal 5D SU(3)(C) x SU(3)(W) model and a unified 5D SU(6) model. In both cases the theory is reduced to the minimal supersymmetric standard model below the compactification scale, with the two Higgs doublets arising from the 5D gauge multiplet. Quarks and leptons are introduced in the bulk, giving Yukawa couplings without conflicting with higher-dimensional gauge invariance. Despite the fact that they arise from higher-dimensional gauge interactions, the sizes of these Yukawa couplings can be different from the 4D gauge couplings due to wave-function profiles of the matter zero modes determined by bulk mass parameters. All unwanted fields are made heavy by introducing appropriate matter and superpotentials on branes, which are also the source of intergenerational mixings in the low-energy Yukawa. matrices. The theory can accommodate a realistic structure for the Yukawa couplings as well as small neutrino masses. Scenarios for supersymmetry breaking and the mu-term generation are also discussed. (C) 2003 Elsevier Science B.V. All rights reserved.