In determining the predictions of the minimal supersymmetric model, the renormalization-group equations must be used to evolve the parameters from the unification scale to the weak scale. Occasionally, an approximation has been used which eliminates the need for numerical solution of the renormalization-group equations. In this Brief Report, we examine the validity of this approximation, in light of the increasing lower bound to the top-quark mass. It is shown that the approximation is very good at determining the top-quark Yukawa coupling, reasonably good at determining the top-quark mass and mass splittings between scalar quarks, and very poor at determining the scalar quark masses, Higgs-boson masses, and various mixing angles.

• Received 29 August 1990

DOI:https://doi.org/10.1103/PhysRevD.43.948