Unified explanation of quark and lepton masses and mixings in the supersymmetric SO(10) model

We discussed neutrino masses and mixings in the SUSY SO(10) model where quarks and leptons have Yukawa couplings to at least two 10 and one 126̄ 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 seesaw mechanism. We show that there are various solutions to reproduce a large mixing angle for ν_μ-ν_τ and a small mixing angle for νₑ-ν_μ, as well as the hierarchical mass spectrum of neutrinos.