S. M. Bilenky

Phenomenology of neutrino oscillations

Abstract This review is focused on neutrino mixing and neutrino oscillations in the light of the recent experimental developments. After discussing possible types of neutrino mixing for Dirac and Majorana neutrinos and considering in detail the phenomenology of neutrino oscillations in vacuum and matter, we review all existing evidence and indications in favour of neutrino oscillations that have been obtained in the atmospheric, solar and LSND experiments. We present the results of the analyses of the neutrino oscillation data in the framework of mixing of three and four massive neutrinos and investigate possibilities to test the different neutrino mass and mixing schemes obtained in this way. We also discuss briefly future neutrino oscillation experiments.

Neutrino mass spectrum from the results of neutrino oscillation experiments

All the possible schemes of neutrino mixing with four massive neutrinos inspired by the existing experimental indications in favor of neutrino mixing are considered in a model independent way. Assuming that in short-baseline experiments only one mass-squared difference is relevant, it is shown that the scheme with a neutrino mass hierarchy is not compatible with the experimental results. Only two schemes with two pairs of neutrinos with close masses separated by a mass difference of the order of 1 eV are in agreement with the results of all experiments. One of these schemes leads to possibly observable effects in3H and (β,β)oν experiments.

NEUTRINOLESS DOUBLE-BETA DECAY: A BRIEF REVIEW

In this brief review we discuss the generation of Majorana neutrino masses through the seesaw mechanism, the theory of neutrinoless double-beta decay, the implications of neutrino oscillation data for the effective Majorana mass, taking into account the recent Daya Bay measurement of ϑ13, and the interpretation of the results of neutrinoless double-beta decay experiments.

Constraints from neutrino oscillation experiments on the effective Majorana mass in neutrinoless double beta decay

Abstract We determine the possible values of the effective Majorana neutrino mass |〈m〉|=| ∑ j U ej 2 m j | in the different phenomenologically viable three and four-neutrino scenarios. The quantities U αj ( α = e , μ , τ ,…) denote the elements of the neutrino mixing matrix and the Majorana neutrino masses m j ( j =1,2,3,…) are ordered as m 1 2 Assuming m 1 ≪ m 3 in the three-neutrino case and m 1 ≪ m 4 in the four-neutrino case, we discuss, in particular, how constraints on |〈 m 〉| depend on the mixing angle relevant in solar neutrino oscillations and on the three mass-squared differences obtained from the analyses of the solar, atmospheric and LSND data. If neutrinoless double β -decay proceeds via the mechanism involving |〈 m 〉|, conclusions about neutrinoless double β -decay can be drawn. If one of the two viable four-neutrino schemes (Scheme A) is realized in nature, |〈 m 〉| can be as large as 1 eV and neutrinoless double β -decay could possibly be discovered in the near future. In this case a Majorana CP phase of the mixing matrix U could be determined. In the other four-neutrino scheme (Scheme B) there is an upper bound on |〈 m 〉| of the order of 10 −2 eV. In the case of three-neutrino mixing the same is true if the neutrino mass spectrum is hierarchical, however, if there exist two quasi-degenerate neutrinos and the first neutrino has a much smaller mass, values of |〈 m 〉| as large as ∼0.1 eV are possible.

Absolute values of neutrino masses: status and prospects

Abstract Compelling evidences in favor of neutrino masses and mixing obtained in the last years in Super-Kamiokande, SNO, KamLAND and other neutrino experiments made the physics of massive and mixed neutrinos a frontier field of research in particle physics and astrophysics. There are many open problems in this new field. In this review we consider the problem of the absolute values of neutrino masses, which apparently is the most difficult one from the experimental point of view. We discuss the present limits and the future prospects of β-decay neutrino mass measurements and neutrinoless double-β decay. We consider the important problem of the calculation of nuclear matrix elements of neutrinoless double-β decay and discuss the possibility to check the results of different model calculations of the nuclear matrix elements through their comparison with the experimental data. We discuss the upper bound of the total mass of neutrinos that was obtained recently from the data of the 2dF Galaxy Redshift Survey and other cosmological data and we discuss future prospects of the cosmological measurements of the total mass of neutrinos. We discuss also the possibility to obtain information on neutrino masses from the observation of the ultra high-energy cosmic rays (beyond the GZK cutoff). Finally, we review the main aspects of the physics of core-collapse supernovae, the limits on the absolute values of neutrino masses from the observation of SN1987A neutrinos and the future prospects of supernova neutrino detection.

Strangeness in the nucleon: neutrino-nucleon and polarized electron-nucleon scattering

Abstract After the EMC and subsequent experiments at CERN, SLAC and DESY on the deep inelastic scattering of polarized leptons on polarized nucleons, it is now established that the Q 2 =0 value of the axial strange form factor of the nucleon, a quantity which is connected with the spin of the proton and is quite relevant from the theoretical point of view, is relatively large. In this review, we consider different methods and observables that allow one to obtain information on the strange axial and vector form factors of the nucleon at different values of Q 2 . These methods are based on the investigation of the neutral current induced effects such as the P-odd asymmetry in the scattering of polarized electrons on protons and nuclei, the elastic neutrino (antineutrino) scattering on protons and the quasi-elastic neutrino (antineutrino) scattering on nuclei. We discuss in detail the phenomenology of these processes and the existing experimental data.

Four-neutrino mass spectra and the Super-Kamiokande atmospheric up-down asymmetry

In the framework of schemes with mixing of four massive neutrinos, which can accommodate the atmospheric, solar and LSND ranges of

Majorana neutrinos, neutrino mass spectrum, CP violation and neutrinoless double beta decay. 2. Mixing of four neutrinos

ensuremath{Delta}{m}^{2}

Implications of CHOOZ results for the decoupling of solar and atmospheric neutrino oscillations

and contain three active neutrinos and a sterile one, we show that, in the whole region of

Constraints on |Ue3|2 from a three-neutrino oscillation analysis of the CHOOZ data

ensuremath{Delta}{m}_{mathrm{LSND}}^{2}