Fermion masses in a string-inspired 4-2-2 model

By Thomas Dent, University of Ioannina

We consider fermion masses in a unified model with Pati-Salam gauge group, where the gauge representations are only fundamentals or singlets, as in the simplest string models. The possibility of taking different sums over SU(4) and SU(2)_R indices allows us to fit all quark and lepton mass matrices, given a U(1) flavour symmetry and an additional gauge singlet. We naturally obtain large neutrino mixing angles. We find a normal hierarchy of light neutrino masses and a small but nonzero U_e3. D=5 proton decay operators are absent and other sources of B and L violation are suppressed.