Unified Explanation of Quark and Lepton Masses and Mixings in the Supersymmetric SO(10) Model

We discussed neutrino masses and mixings in SUSY SO(10) model where quarks and leptons have Yukawa couplings to at least two 10 and one $\bar{126}$ Higgs scalars. In this model, the Dirac and the right-handed Majorana mass terms are expressed by linear combinations of quark and charged lepton mass matrices, which then determine the neutrino mass matrix by the see-saw mechanism. We show that there are various solutions to reproduce a large mixing angle for $\nu_\mu-\nu_\tau$ and a small mixing angle for $\nu_e-\nu_\mu$, as well as the hierarchical mass spectrum of neutrinos.