Universal Seesaw Mass Matrix Model with Three Light Pseudo-Dirac Neutrinos

Abstract

A universal seesaw mass matrix model, which gives successful description of quark mass matrix in terms of lepton masses, yields three "sterile" neutrinos ν^s_{i}, which compose pseudo-Dirac neutrinos ν_{i\pm}^{ps}\simeq (ν_{i} \pm ν^s_{i})/\sqrt{2} together with the active neutrinos ν_{i} (i=e,μ,τ). The solar and atmospheric neutrino data are explained by the mixings ν_{e}\leftrightarrow ν^s_{e} and ν_μ\leftrightarrow ν^s_μ, respectively. In spite of such observations of the large mixing \sin^2 2θ\simeq 1 in the disappearance experiments, effective mixing parameters \sin^2 2θ^{αβ} in appearance experiments ν_α\toν_β(α, β= e, μ, τ) are highly suppressed.