Oscillations of solar and atmospheric neutrinos

Motivated by recent results from SuperKamiokande, we study both solar andatmospheric neutrino fluxes in the context of oscillations of the three knownneutrinos. We aim at a global view which identifies the various possibilities,rather than attempting the most accurate determination of the parameters ofeach scenario. For solar neutrinos we emphasise the importance of performing ageneral analysis, independent of any particular solar model and we consider thepossibility that any one of the techniques --- chlorine, gallium or waterCerenkov --- has a large unknown systematic error, so that its results shouldbe discarded. The atmospheric neutrino anomaly is studied by paying specialattention to the ratios of upward and downward going nu_e and nu_mu fluxes.Both anomalies can be described in a minimal scheme where the respectiveoscillation frequencies are widely separated or in non-minimal schemes with twocomparable oscillation frequencies. We discuss explicit forms of neutrino massmatrices in which both atmospheric and solar neutrino fluxes are explained. Inthe minimal scheme we identify only two `zeroth order' textures that can resultfrom unbroken symmetries. Finally we discuss experimental strategies for thedetermination of the various oscillation parameters.Comment: 20 pages, 7 figures. Final version: one reference added; fit of atmospheric neutrinos improve