INFRARED STABLE FIXED-POINTS OF YUKAWA COUPLINGS IN SUPERSYMMETRIC MODELS

We provide the solutions of the fixed point conditions of the Yukawa s ector for a large class of N = 1 supersymmetric theories including the minimal and next-to-minimal supersymmetric standard models and their grand unified and other extensions. We also introduce a test which can discriminate between infra-red stable, infra-red unstable and saddle point solutions, and illustrate our methods with the example of the ne xt-to-minimal supersymmetric standard model. We show that in this case , the fixed point prediction of the top quark mass is equivalent to th at of the minimal supersymmetric standard model, supporting previous n umerical analyses. (C) 1997 Elsevier Science B.V.