Neutrino Oscillations Induced by Two-loop Radiative Effects

抄録

Phenomena of neutrino oscillations are discussed on the basis of two-loop radiative neutrino mechanism. Neutrino mixings are experimentally suggested to be maximal in both atmospheric and solar neutrino oscillations. By using L_e - L_μ - L_τ (≡ L')-conservation, which, however, only ensures the maximal solar neutrino mixing, we find that two-loop radiative mechanism dynamically generates the maximal atmospheric neutrino mixing and that the estimate of Δm^2_&odot;/Δm^2_<atm>〜εm_e/m_τ explains Δm^2_&odot;/Δm^2_<atm> ≪ 1 because of m_e/m_τ ≪ 1, where ε measures the breaking of the L'-conservation. Together with Δm^2_<atm> &ap; 3× 10^<-3> eV^2, this estimate yields Δm^2_&odot;〜10^<-7> eV^2 for ε〜0.1, which corresponds to the LOW solution to the solar neutrino problem. Neutrino mass scale is given by (16π^2)^<-2>m_e,m_τ/M (M〜1 TeV), which is of order 0.01 eV.