A two-loop finite supersymmetric SU5 theory: Towards a theory of fermion masses

We present a realistic two-loop finite supersymmetric grand unified theory. The gauge group is SU5 and the low energy theory includes three families of quarks and leptons with the minimal Higgs doublet content. The most important feature of the model is the non-trivial constraint of finiteness on the quark and lepton masses. We find sin2thetasub(w) = 0.21 and msub(b)/msub(tau) = 1.8 (at Msub(w)) and predict a top quark mass of 155 GeV. Nucleon decay is dominated by colored Higgs triplet exchange with characteristic decay modes p -> K0μ+, p -> K+anti νsub(μ) and n -> K0anti νsub(μ). (orig.)