Early years of neutrino oscillations
The first papers on neutrino oscillations are shortly reviewed.
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arXiv subjects
S. M. Bilenky
Publications and source records attributed to S. M. Bilenky.
Constraints from Neutrino Oscillation Experiments on the Effective Majorana Mass in Neutrinoless Double $β$-Decay
We determine the possible values of the effective Majorana neutrino mass $|< m > |= |\sum_j U_{ej}^2 m_j|$ 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 < m_2 < ... $ Assuming $m_1 \ll m_3$ in the three-neutrino case and $m_1 \ll m_4$ 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 $\sim 0.1$ eV are possible.
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Summary of the NOW'98 Phenomenology Working Group
Summary of the Phenomenology Working Group at the Europhysics Neutrino Oscillation Workshop (NOW'98), 7-9 September 1998, Amsterdam.
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Phenomenology of Neutrino Oscillations
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.
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Sterile neutrinos?
The notion of sterile neutrinos is discussed. The schemes of mixing of four massive neutrinos, which imply the existence of sterile neutrinos, are briefly considered. Several model independent methods that allow to reveal possible transitions of solar neutrinos into sterile states are presented.
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New developments in neutrino physics
A review of the problem of neutrino mass, mixing and oscillations is given. Possible phenomenological schemes of neutrino mixing are discussed. The most important consequences of neutrino mixing--neutrino oscillations are considered in some details. The data of atmospheric, solar and LSND experiments are discussed. The results of phenomenological analyses of the data under the assumption of the mixing of three and four massive neutrinos are shortly presented.
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Neutrino oscillation constraints on neutrinoless double-beta decay
It is shown that, in the framework of the scheme with three-neutrino mixing and a mass hierarchy, the results of neutrino oscillation experiments imply an upper bound of about 10^{-2} eV for the effective Majorana mass in neutrinoless double-beta decay. The schemes with four massive neutrinos are also briefly discussed.
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Four-neutrino spectrum from oscillation data
It is shown that the Super-Kamiokande atmospheric up--down asymmetry, together with the results of all other neutrino oscillation experiments, allows to constraint the possible spectra of four massive neutrinos. The two schemes with two pairs of neutrinos with close masses separated by a gap of about 1 eV are favored by the data.
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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 Delta m^2, we show that, in the whole region of Delta m^2_{LSND} 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.
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Strange form factors of the proton: a new analysis of the neutrino (antineutrino) data of the BNL-734 experiment
We consider ratios of elastic neutrino(antineutrino)-proton cross sections measured by the Brookhaven BNL-734 experiment and use them to obtain the neutral current (NC) over charged current (CC) neutrino-antineutrino asymmetry. We discuss the sensitivity of these ratios and of the asymmetry to the electric, magnetic and axial strange form factors of the nucleon and to the axial cutoff mass M_A. We show that the effects of the nuclear structure and interactions on the asymmetry and, in general, on ratios of cross sections are negligible. We find some restrictions on the possible values of the parameters characterizing the strange form factors. We show that a precise measurement of the neutrino-antineutrino asymmetry would allow the extraction of the axial and vector magnetic strange form factors in a model independent way. The neutrino-antineutrino asymmetry turns out to be almost independent on the electric strange form factor and on the axial cutoff mass.
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Four-Neutrino Mixing, Oscillations and Big-Bang Nucleosynthesis
We investigate the implications of the standard Big-Bang Nucleosynthesis constraint on the number of light neutrinos in the framework of the two four-neutrino schemes that are favored by the results of neutrino oscillation experiments.
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Neutrino mass spectrum and mixing from neutrino oscillation data
Two schemes of mixing of four massive neutrinos with two close neutrino masses separated by a gap of Delta m^2 about 1 eV^2 can accommodate solar, atmospheric and LSND neutrino oscillation data. It is shown that long-baseline nu(e)->nu(x) and nu(mu)->nu(e) transitions are strongly suppressed in these schemes. The scheme of mixing of three massive neutrinos with a mass hierarchy that can describe solar and atmospheric data is also discussed. It is shown that in this scheme the effective Majorana mass that characterizes the matrix element of neutrinoless double-beta decay is smaller than about 10^{-2} eV.
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Four-neutrino mixing, oscillations and BBN
We investigate the implications for neutrino mixing implied by the results of all neutrino oscillation experiments and by the standard Big-Bang Nucleosynthesis constraint on the number of light neutrinos.
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On the neutrino mass spectrum and neutrino mixing from oscillation data
Two schemes of mixing of four massive neutrinos with two couples of close neutrino masses separated by a gap of the order of 1 eV can accommodate solar, atmospheric and LSND neutrino oscillation data. It is shown that long-baseline nu(e)->nu(e) and nu(mu)->nu(e) transitions are strongly suppressed in these schemes. The scheme of mixing of three neutrino masses with a mass hierarchy that can describe solar and atmospheric neutrino data is also discussed. It is shown that in this scheme the effective Majorana mass | | that characterizes the matrix element of neutrinoless double-beta decay is less than 10^{-2} eV.
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The ratio of p and n yields in NC neutrino(antineutrino)-nucleus scattering and strange form factors of the nucleon
We calculate the ratio of proton and neutron yields in NC induced neutrino(antineutrino)-nucleus inelastic scattering at neutrino energies of about 1 GeV. We show that this ratio depends very weakly on the nuclear models employed and that in the neutrino and antineutrino cases the ratios have different sensitivity to the axial and vector strange form factors; moreover, the ratio of antineutrino--nucleus cross sections turns out to be rather sensitive to the electric strange form factor. We demonstrate that measurements of these ratios will allow to get information on the strange form factors of the nucleon in the region Q > 0.4 GeV^2.
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Neutrino masses and mixing
We present a short review of the present status of the problem of neutrino masses and mixing. The existing experimental results indicate that there are at least four massive neutrinos. We show that only two schemes with mixing of four neutrinos and mass spectra in which two groups of close masses are separated by the ``LSND gap'' (~ 1 eV) are compatible with the results of all neutrino oscillation experiments. We discuss different consequences of these schemes for future neutrino oscillation experiments.
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Four-neutrino mixing and long-baseline neutrino oscillation experiments
We consider the two schemes with four massive neutrinos which are compatible with the results of all neutrino oscillation experiments. We show that in these two schemes the probabilities of nu_e disappearance and nu_mu->nu_e appearance in long-baseline experiments are strongly suppressed.
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Neutrino Masses and Mixings in the Light of Experimental Data
All the possible schemes of neutrino mixing with four massive neutrinos inspired by the existing experimental indications in favour of neutrino mixing are considered. It is shown that the scheme with a neutrino mass hierarchy is not compatible with the experimental results, likewise all other schemes with the masses of three neutrinos close together and the fourth mass separated by a gap needed to incorporate the LSND neutrino oscillations. Only two schemes with two pairs of neutrinos with close masses separated by this gap of the order of 1 eV are in agreement with the results of all experiments. We carefully examine the arguments leading to this conclusion and also discuss experimental consequences of the two favoured neutrino schemes.
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