Oscillation characteristics of active and sterile neutrinos and neutrino anomalies at shot distances

Abstract

A generalized phenomenological (3 + 2 + 1)-model with three active and three sterile neutrinos is considered for the calculation of the neutrino oscillation characteristics at normal mass hierarchy of active neutrinos and significant splitting between the mass of one sterile neutrino and the masses of other two sterile neutrinos. A new parametrization and a certain form of the general neutrino mixing matrix for active and sterile neutrinos are suggested taking into account the possible violation of CP invariance in the lepton sector. The test values of the neutrino masses and the mixing parameters are chosen. The transition probabilities for the different flavors of neutrino, which can be transformed into each other, are calculated, and the graphical dependences are obtained for the disappearance probability of muon neutrino/antineutrino and appearance probability of electron neutrino/antineutrino in the muon neutrino/antineutrino jet as a function of distance and other model parameters at their acceptable values and at neutrino energies not higher than 50 MeV, as well as a function of the ratio of the distance to the neutrino energy. It is shown that in the case of the mixing matrix of a definite type (of the a_2 type) between active and sterile neutrinos the explanation of the acceleration anomaly on small distances in the neutrino data (LSND anomaly) is possible, as well as the reactor and gallium anomalies. The theoretical results obtained can be used for the interpretation and prediction of results of the ground-based neutrino experiments on searching for the sterile neutrinos, and also for the analysis of certain astrophysical observation data.