Higgs mass in the gauge-Higgs unification

The gauge-Higgs unification theory identifies the zero mode of the extra-dimensional component of the gauge field as the usual Higgs doublet. Since this degree of freedom is the Wilson line phase, the Higgs does not have the mass term nor quartic coupling at the tree level. Through quantum corrections, the Higgs can take a vacuum expectation value, and its mass is induced. The radiatively induced mass tends to be small, although it can be lifted to O(100) GeV by introducing the O(10) numbers of bulk fields. Perturbation theory becomes unreliable when a large number of bulk fields are introduced. We reanalyze the Higgs mass based on useful expansion formulae for the effective potential and find that even a small number of bulk field can have the suitable heavy Higgs mass. We show that a small (large) number of bulk fields are enough (needed) when the SUSY breaking mass is large (small). We also study the case of introducing the soft SUSY breaking scalar masses in addition to the Scherk-Schwarz SUSY breaking and obtain the heavy Higgs mass due to the effect of the scalar mass. (c) 2005 Elsevier B.V. All rights reserved.