Oscillation properties of active and sterile neutrinos and neutrino anomalies at short 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 a2 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.

Neutrino fluxes from a core-collapse supernova in a model with three sterile neutrinos

“…Let us give the basic principles of the phenomenological (3 + 2 + 1) model of neutrinos that is used below to calculate the effects involving three StN (Zysina et al 2014; Khruschov et al , 2016. In this model two StN are approximately degenerate in mass, while the mass of the third StN can differ significantly from the masses of the two other ones.…”

“…One of such models is the (3 + 1 + 2) model (or (3 + 2 + 1) model) that contains three StN, two of which are approximately degenerate in mass, while the mass of the third one can differ significantly from the masses of the two other ones (Zysina et al 2014; . Within the (3 + 2 + 1) model with three StN the AcN and StN mass characteristics were estimated (Zysina et al 2014), the AcN and StN appearance and survival probabilities in the Sun were calculated by taking into account the coherent scattering of neutrinos in matter , and various AcN and StN mixing matrices were considered to explain the neutrino anomalies at small distances (Khruschov et al 2016). considered the change in neutrino flavor composition due to coherent neutrino scattering by electrons and neutrons of superdense matter in the model with three StN.…”

“…The observations of cosmological cosmic microwave background fluctuations within the framework of standard cosmological models limit the number of new light neutrinos virtually to one (see, e.g., Komatsu et al 2011;Ade et al 2013). Nevertheless, just as in Zysina et al (2014), , and Khruschov et al ( , 2016, we will consider a model with three AcN and three StN. Let us list several reasons for such a choice.…”

“…These include, first, the principle of left-right symmetry noted above, which may be restored on a scale exceeding the scale of spontaneous electroweak symmetry breaking, ∼ 1 TeV. In addition, the form of the AcN and StN mixing matrix chosen under strict unitarity conditions in Khruschov et al (2016) necessitates introducing three StN. Even if the derived cosmological constraints on the total number of relativistic neutrinos are taken into account, it should be noted that these constraints are model-dependent.…”

A short travel for neutrinos in Large Extra Dimensions

“…Here we focus on Large Extra Dimensions (LED) and the possibility that its signals be differentiated from the sterile hypothesis at the SBN program. Other proposals can be tested in SBN facility for instance the search for multiple sterile states [18][19][20] and MeV-scale sterile decay [21][22][23].…”