Fermion Mass Hierarchy and Proton Stability from Non-anomalous U(1)_F in   SUSY SU(5)
  We present a realistic supersymmetric SU(5) model combined with a non-anomalous U(1)_F symmetry. We find a set of U(1)_F charges which automatically lead to the realistic mass hierarchy and mixing patterns for quarks, leptons and neutrinos. All gauge anomalies, including the [U(1)_F]^3 anomaly, are cancelled in our model without invoking the Green-Schwarz mechanism or having exotic fields. Proton decay mediated by dimension 5 operators is automatically suppressed in our model, because the scale set by the largest right-handed neutrino mass is much less than the GUT scale. 
Mu-Chun Chen, D. R. Timothy Jones, Arvind Rajaraman, Hai-Bo Yu