Universal seesaw mass matrix model with three light pseudo Dirac neutrinos

A universal seesaw mass matrix model, which gives a successful description of the quark mass matrix in terms of lepton masses, yields three “sterile” neutrinos ${\nu }_i^s,$ which compose pseudo-Dirac neutrinos ${\nu }_{i\pm }^{\mathrm{ps}}\simeq ({\nu }_i\pm {\nu }_i^s)/\sqrt{2}$ together with active neutrinos ${\nu }_i(i=e,\mu ,\tau ).\mathrm{}$ The solar and atmospheric neutrino data are explained by the mixings ${\nu }_e\leftrightarrow {\nu }_e^s$ and ${\nu }_{\mu }\leftrightarrow {\nu }_{\mu }^s,$ respectively. In spite of such observations of the large mixing ${\sin }^{2}2\theta \simeq 1$ in the disappearance experiments, effective mixing parameters ${\sin }^{2}2{\theta }^{\alpha \beta }$ in appearance experiments ${\nu }_{\alpha }\to {\nu }_{\beta }(\alpha ,\beta =e,\mu ,\tau )$ are highly suppressed.