Atmospheric and Solar neutrinos in the light of the SuperKamiokande results

Abstract

The hierarchy $\Delta m^2_{atm} \gg \Delta m^2_\odot$ and the large $\theta_{23}$ mixing angle, as suggested by neutrino oscillation experiments, can be accounted for by a variety of lepton flavour models. A dichotomy emerges: i) Models were all neutrino masses are bounded by $m_{atm}\equiv (\Delta m^2_{atm})^{1/2}\approx 0.03 eV$; ii) Models of quasi-degenerate neutrinos. It is shown how these different patterns of neutrino masses may arise from different lepton flavour symmetries. Physical implications are discussed in the various cases.