2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/139828In SO(10) models with a vectorial fourth generation of down quarks and leptons, the structure of the neutrino Majorana and Dirac mass matrices generically coincide with those of up- and down-quarks, respectively. Then the small neutrino mass hierarchy follows from the mismatch of the up and down quark mass hierarchies and we can accommodate naturally a normal hierarchy. The effective CP violating phases in the quark sector, neutrino oscillations and leptogenesis are unrelated.Submitted for the SUSY07 proceedings, 4 pagesHigh Energy Physics - Phenomenologytext