Quark, Lepton and Neutrino Masses In Horava-Witten Inspired Models
  Horava-Witten M-Theory offers new ways in achieving the quark and lepton mass hierarchies not naturally available in supergravity unified models. In previous work, based on a torus fibered Calabi-Yau manifold with a del Pezzo base dP_7,a three generation SU(5)model with Wilson line breaking to the Standard Model was constructed. It was seen that if the additional 5- branes clustered near the distant orbifold plane, it was possible that such models could generate the observed hierarchies of quark masses without undue fine tuning. We update these results here and extend them to include the charged leptons. A new mechanism for generating small neutrino masses (different from the ususal seesaw mechanism)arises naturally from a possible cubic holomorphic term in the Kahler potential when supersymmetry is broken. We show that the LMA solution to neutrino masses can occur, with a good fit to all neutrino oscillation data. The model implies the existance of the \mu -> e \gamma decay even for universal slepton soft breaking masses, at rates accessible to the next round of experiments. 
R. Arnowitt, B. Dutta and B. Hu