INFRARED FIXED-POINT STRUCTURE CHARACTERIZING SUSY SU(5) SYMMETRY-BREAKING

We analyze the one-loop renormalisation group equations for the parame ters of the Higgs potential of a supersymmetric SU(5) model with first step of symmetry breaking involving an adjoint Higgs. In particular, we investigate the running of the parameters that decide the first ste p of symmetry breaking in an attempt to establish which symmetry-break ing scenarios would be most likely if the model is the effective low-e nergy description of some more fundamental theory. An infra-red fixed point is identified analytically. We show that it is located at the bo undary between the region of Higgs parameter space corresponding to un broken SU(5) and the region corresponding to the breaking of SU(5) to the Standard Model, and we elaborate on its implications. We also obse rve that certain forms of the Higgs potential discussed at tree level in the literature are not renormalisation group invariant.