Muon anomalous magnetic moment and τ→μγ in a realistic string-inspired model of neutrino masses

We discuss the lepton sector of a realistic string-inspired model based on the Pati-Salam SU(4) x SU(2)(L) x SU(2)(R) gauge group supplemented by a U(I) family symmetry. The model involves third family Yukawa unification, predicts large tan beta similar to 50, and describes all fermion masses and mixing angles, including approximate bi-maximal mixing in the neutrino sector. Atmospheric neutrino mixing is achieved via a large 23 entry in the neutrino Yukawa matrix which can have important phenomenological effects. We find that the recent BNL result on the muon (g - 2) can be easily accommodated in a large portion of the SUSY parameter space of this model. Over this region of parameter space the model predicts a CP-even Higgs mass near 115 GeV, and a rate for tau --> mu + gamma which is close to its current experimental limit. (C) 2001 Elsevier Science B.V. All rights reserved.