C. Giunti

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.

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.

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

Short-baseline neutrino oscillations and ( beta beta )0 nu decay in schemes with an inverted mass spectrum.

\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

Light Sterile Neutrinos: Status and Perspectives

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

Electromagnetic form factors of the nucleon: new fit and analysis of uncertainties

allowed by LSND, the Super-Kamiokande up-down asymmetry excludes all mass spectra with a group of three close neutrino masses separated from the fourth mass by the LSND gap of order 1 eV. Only two schemes with mass spectra in which two pairs of close masses are separated by the LSND gap can describe the Super-Kamiokande up-down asymmetry and all other existing neutrino oscillation data.

Four-neutrino mixing and Big-Bang Nucleosynthesis

We have considered short-baseline neutrino oscillations, tritium beta-decay and neutrinoless double-beta decay in two schemes with an inverted mass spectrum and mixing of three and four massive neutrino fields. We have analyzed the results of the latest experiments on the search for oscillations of terrestrial neutrinos and we have discussed the compatibility of the LSND indication in favor of neutrino oscillations with the results of the other experiments. In the framework of the models under consideration, it is shown that the observation of neutrinoless double-beta decay could allow to obtain information about the CP violation in the lepton sector.

Inelastic ν and ν scattering on nuclei and “strangeness” of the nucleon

Abstract We have considered the results of solar and atmospheric neutrino oscillation experiments in the scheme of mixing of three neutrinos with a mass hierarchy. It is shown that (if m 3 2 −m 1 2 >10 −3 eV 2 ) the recent results of the CHOOZ experiment imply that |Ue3|2≪1 (U is the neutrino mixing matrix), that the oscillations of solar neutrinos are described by the two-generation formalism and that the oscillations of solar and atmospheric neutrinos decouple. It is also shown that if not only |Ue3|2≪1 but also |Ue3|≪1, then the oscillations of atmospheric neutrinos do not depend on matter effects and are described by the two-generation formalism. In this case, with an appropriate identification of the mixing parameters, the two-generation analyses of solar and atmospheric neutrino data provide direct information on the mixing parameters of three neutrinos. We discuss the possibility to get information on |Ue3|2 in long-baseline neutrino oscillation experiments.

Neutrino oscillations in the framework of three generation mixings with mass hierarchy

Abstract The indications in favor of the existence of light sterile neutrinos at the eV scale found in short-baseline neutrino oscillation experiments is reviewed. The future perspectives of short-baseline neutrino oscillation experiments and the connections with β -decay measurements of the neutrino masses and with neutrinoless double- β decay experiments are discussed.