Democratic Universal Seesaw Model with Three Light Sterile Neutrinos

Abstract

Based on the "democratic" universal seesaw model, where mass matrices $M_f$ of quarks and leptons f_i (f=u,d,ν,e; i=1,2,3) are given by a seesaw form M_f\simeq -m_L M_F^{-1} m_R, and m_L and m_R are universal for all the fermion sectors, and the mass matrices M_F of hypothetical heavy fermions F_i have a democratic structure, a possible neutrino mass matrix is investigated. In the model, there are three sterile neutrinos ν_{iR} which mix with the active neutrinos ν_{iL} with θ\sim 10^{-2} and which are harmless for constraint from the bib bang nucleosynthesis. The atmospheric, solar and LSND neutrino data are explained by the mixings ν_{μL} \leftrightarrowν_{τL}, ν_{eL}\leftrightarrow ν_{eR} and ν_{eL}\leftrightarrow ν_{μL}, respectively. The model predicts that Δm^2_{solar}/Δm^2_{atm} \simeq (R^2-1) m_e/\sqrt{m_μm_τ} [R=m(ν_{iR})/m(ν_{iL}) (i=1,2,3)] with \sin^{2}2θ_{atm}\simeq 1 and Δm_{LSND}^2/Δm^2_{atm} \simeq (1/4)\sqrt{m_μ/m_e} with \sin^2 2θ_{LSND} \simeq 4m_e/m_μ.