Tree-Level Nondecoupling and the Supersymmetric Higgs Sector

Abstract

Because of the existence of cubic scalar couplings, there are in general nondecoupling effects at tree level in the scalar sector of any theory with two or more very different mass scales. We show this explicitly in the minimal nonsupersymmetric SU(5) model of grand unification. We show also how tree-level decoupling is guaranteed if supersymmetry is imposed. On the other hand, if the gauge symmetry is larger than that of the standard model at the mass scale of supersymmetry breaking, the two-Higgs-doublet structure at the presumably lower electroweak energy scale will be different from that of the minimal supersymmetric standard model, as shown already previuosly in a number od specific examples. We add here one example involving four Higgs doublets.