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 ≃− 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∼10 −2 and which are harmless for constraint from the big bang nucleosynthesis. The atmospheric, solar and the LSND neutrino data are explained by the mixings ν μL ↔ ν τL , ν eL ↔ ν eR and ν eL ↔ ν μL , respectively. The model predicts that Δm 2 solar /Δm 2 atm ≃(R 2−1)m e/ m μm τ [ R= m( ν iR )/ m( ν iL ) ( i=1,2,3)] with sin 22 θ atm≃1 and Δm LSND 2/Δm 2 atm ≃(1/4) m μ/m e with sin 22 θ LSND≃4 m e / m μ .