On the Status of Neutrino Mixing and Oscillations

Evidences in favor of neutrino oscillations, obtained in the solar and atmospheric neutrino experiments, are discussed. Neutrino oscillations in the solar and atmospheric ranges of the neutrino masssquared differences are considered in the framework of the minimal scheme with the mixing of three massive neutrinos. There exist at present convincing evidences of neutrino oscillations obtained in the atmospheric [1, 2, 3] and in the solar [4, 5, 6, 7, 8, 9, 10, 11, 12] neutrino experiments. We will present here the theory of the neutrino oscillations and existing evidences in favor of oscillations. We will consider neutrino oscillations in the framework of the minimal scheme of the threeneutrino mixing and we will demonstrate that in the leading approximation neutrino oscillations in the atmospheric and solar ranges of the neutrino mass-squared differences are described by the two-neutrino type formulas. 1 Basics of neutrino mixing and oscillations 1. Interaction of neutrinos with matter; flavor neutrinos (a) Investigation of neutrino oscillations is based on the assumption, confirmed by all existing data, that the interaction of neutrinos with matter is given by the Standard Model charged current (CC) Report at the XVI Rencontres de Physique de La Vallee d’Aoste, La Thuile, Aosta Valley (Italy) March 3-9, 2002 The LSND [13] indication in favor of neutrino oscillations requires confirmation. The MiniBooNE experiment [14] at the Fermilab, which aim to check the LSND claim, is going on at present. The first result is planned to be available in 2004.