Two-loop Higgs mass in supersymmetric Kaluza-Klein theories

We perform an explicit two-loop computation of the Higgs mass in a five-dimensional supersymmetric theory compactified on the orbifold S-1/Z(2), with superpotential localized on a fixed-point brane and supersymmetry broken in the bulk of the extra dimension by Scherk-Schwarz boundary conditions. At one-loop, the Higgs mass is finite and proportional to 1/R-,(2) R being the radius of the extra dimension. The two-loop corrections contain finite (proportional to 1/R-2) and linearly divergent (proportional to Lambda /R-2) terms, where Lambda is the cutoff of the five-dimensional theory. The divergent terms are cancelled by diagrams containing one-loop wave-function renormalization counterterms, i.e., by linear threshold effects of Yukawa (and gauge) couplings, at the scale 1/R. As a result there is no counterterm for the Higgs mass, which is finite and calculable to the considered order. (C) 2001 Elsevier Science B.V. All rights reserved.