Neutrino masses and mixings in a universal seesaw mass matrix model

Neutrino masses and mixings are investigated on the basis of a universal seesaw mass matrix model, in which quark (except for the top quark) and charged lepton mass matrices M_f and the neutrino mass matrix M_ν are given by M_f~=m_LM^-1_Fm_R and M_ν~=m_LM^-1_Fm^T_L (F=N), respectively. For a simple model which can successfully describe quark masses and mixings, we find that the observed neutrino data (except for the solar neutrino data) are favorable to the intermediate mass scales O(m_R)=10¹¹ GeV and O(M_F)=10¹³ GeV together with O(m_L)=10² GeV. In spite of the largeness of O(m_R), the observed top-quark mass can be consistently understood from the would-be seesaw mass matrix with these mass scales.