Resonant neutrino oscillations in matter

Abstract

Review is devoted to the systematic representation of the theory (first part) and the applications (second part) of neutrino oscillations in matter. The evolution equations for mixed neutrinos in matter are deduced in different forms and analized. The consideration includes symmetries, limits of applications and some generalizations of equations. The analogies of the mixed neutrinos in matter have been found. We discuss in details the properties and the physical sense of the resonance in a system of mixed neutrinos. For homogeneous matter the effect of resonant enhancement of oscillations is described. Different representation of the adiabaticity condition, which determines a dynamics of neutrino oscillations, are given, and the adiabaticity parameter is introduced. Practically complete transformations of one neutrino species into another one are possible at the adiabatic (or near to adiabatic) crossing of resonance layer even at small vacuum mixing. The effect of non-oscillatory transition is remarked. Some results have been obtained for the adiabaticity violation regime. Also we review the exact solutions of the equations for special density distributions. The generalization of the theory for the case of three neutrino mixing is given. The effects of inelastic collisions as well as the divergence of neutrino wave packets are discussed. The theory of resonant conversion is applied then to the neutrino fluxes inside the Sun, the Earth and the collapsing stars. The distortion of the neutrino energy spectra by the matter filters with different density distributions are calculated. We describe the observable effects of conversion for solar and atmospheric neutrinos as well as for neutrinos from collapsing stars. The searching for these effects is considered as a method of measuring the neutrino masses and mixing. Resonant conversion may quite naturally solve the solar neutrino problem. The distinctions of resonance conversion effects and another mechanisms for solar ν e - flux reduction are considered, and in this connection the possibilities of solar neutrino spectroscopy are outlined. We discuss the consequences of ν - signal detection from supernova 1987A.