In the minimal supersymmetric standard model, the three gauge couplings appear to unify at a mass scale near 2×${10}^{16}$ GeV. We investigate the possibility that intermediate scale particle thresholds modify the running couplings so as to increase the unification scale. By requiring consistency of this scenario, we derive some constraints on the particle content and locations of the intermediate thresholds. There are remarkably few acceptable solutions with a single cleanly defined intermediate scale far below the unification scale.

• Received 11 January 1995

DOI:https://doi.org/10.1103/PhysRevD.51.6515