arXiv subjects
Publications and source records attributed to S. M. Bilenky.
Neutrino mixing and basics of neutrino oscillations are considered. Recent evidences in favour of neutrino oscillations, obtained in the solar and atmospheric neutrino experiments, are discussed. Neutrino oscillations in the solar and atmospheric ranges of $Δm^{2}$ are considered in the framework of the minimal scheme with the mixing of three massive neutrinos.
The existing calculations of the nuclear matrix elements of the neutrinoless double beta-decay differ by about a factor three. This uncertainty prevents quantative interpretation of the results of experiments searching for this process. We suggest here that the observation of the neutrinoless double beta-decay of several nuclei in future experiments of could allow to test different calculations of the nuclear matrix elements through the direct comparison of them with the experimental data.
Evidences in favor of neutrino oscillations, obtained in the solar and atmospheric neutrino experiments, are discussed. Neutrino oscillations in the solar and atmospheric ranges of the neutrino mass-squared differences are considered in the framework of the minimal scheme with the mixing of three massive neutrinos.
The basics of neutrino oscillations is presented. Existing evidences of neutrino oscillations, obtained in the atmospheric and solar neutrino experiments, are considered. The new CHOOZ bound on the element $|U_{e3}|^{2}$, obtained from the three-neutrino analysis of the data, is discussed. Decoupling of neutrino oscillations in the solar neutrino range of $Δm^{2}$ is considered.
Results of a new analysis of the CHOOZ data, performed in the framework of three-neutrino mixing, are presented. Both the cases of normal and inverted neutrino mass hierarchy are considered. The parameters characterizing the solar neutrino oscillations, $Δm^2_{\odot}$ and $θ_{\odot}$, are assumed to lie in the region of the large mixing angle (LMA) MSW solution of the solar neutrino problem. For $Δm^2_{\odot}$ not exceeding $10^{-4} eV^2$ the new CHOOZ exclusion curve in the $Δm^2_{31} - |U_{e3}|^2$ plane practically coincides with the exclusion curve obtained in the two-neutrino mixing case. For $Δm^2_{\odot}$ bigger than or equal to $2x10^{-4} eV^2$, the constraints of the CHOOZ data on $|U_{e3}|^2$ are more stringent than those obtained in the two- neutrino oscillation analysis.
A short review of the status of neutrino mixing and neutrino oscillations is given. The basics of neutrino mixing and oscillations is discussed. The latest evidences of neutrino oscillations obtained in the Super-Kamiokande and the SNO solar neutrino experiments and in the Super-Kamiokande atmospheric neutrino experiment are considered. The results of solar and atmospheric neutrino experiments are discussed from the point of view of the three-neutrino mixing.
All existing solar and atmospheric neutrino oscillation data are described by the standard two-neutrino formulas with neutrino mass squared differences that satisfy the hierarchy relation $Δm^{2}_{sol} \ll Δm^{2}_{atm}$. We discuss this phenomenon from the point of view of three-neutrino mixing. Possibilities to see effects of three-neutrino mixing and, in particular, effects of CP-violation in the lepton sector depend on the values of $|U_{e3}|^2 $ and $Δm^{2}_{sol}$. We present an upper bound of $|U_{e3}|^2 $, which was obtained from a three-neutrino analysis of CHOOZ data in the case if the solar neutrino oscillation parameters lie in the LMA allowed region.
Using the recent result of the SNO solar neutrino experiment, we have demonstrated in a model independent way that the contribution of Be-7 and other medium energy neutrinos to the event rate of the Homestake experiment is 4 sigma smaller than the BP2000 SSM prediction. We have considered the implications of this result for the future BOREXINO experiment.
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 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 details the phenomenology of these processes and the existing experimental data.
Assuming mixing of three massive Majorana neutrinos, we study the implications of the neutrino oscillation solutions of the solar and atmospheric neutrino problems and of the results of the CHOOZ experiment for the predictions of the effective Majorana mass in neutrinoless double beta decay, |< m >|. The general case of CP-nonconservation is investigated. The predicted values of |< m >|, depend strongly on the type of the neutrino mass spectrum, on the solution of the solar neutrino problem, as well as on the values of the two Majorana CP-violating phases, present in the lepton mixing matrix. We find that i) $|< m >| \lesssim 0.02 $eV for a hierarchical neutrino mass spectrum, ii) $|< m >| \lesssim 0.09 $eV if the spectrum is of the inverted hierarchy type, and iii) $|< m >| \leq m$ in the case of three quasi-degenerate neutrinos, m > 0 being the common neutrino mass scale which is limited by the bounds from the $^3$H $β-$decay experiments, $m < 2.5 $eV. The observation of the $(ββ)_{0ν}-$decay with a rate corresponding to $|< m >| \gtrsim 0.02 $eV can provide unique information on the neutrino mass spectrum and on the CP-violation in the lepton sector, and if CP-invariance holds - on the relative CP-parities of the massive Majorana neutrinos.
Assuming four-neutrino mixing and massive Majorana neutrinos, we study the implications of the neutrino oscillation solutions of the solar and atmospheric neutrino problems, of the results of the LSND experiment and of the constraints on neutrino oscillations, obtained in reactor and accelerator experiments, for the predictions of the effective Majorana mass in neutrinoless double beta (\betabeta-)decay, \meff. All 4-neutrino mass spectra compatible with the existing neutrino mass and oscillation data are considered. The general case of CP-nonconservation is investigated. We have also analyzed in detail the question of whether a measurement of $\meff \gtap 0.01$ eV in the next generation of \betabeta-decay experiments (NEMO3, CUORE, EXO, GENIUS), combined with the data from the solar, atmospheric, reactor and accelerator neutrino oscillation experiments and from the future neutrino mass $^3$H $β-$decay experiment KATRIN would allow, and under what conditions, i) to determine the absolute values of the neutrino masses and thus the neutrino mass spectrum, and ii) to establish the existence of CP-violation in the lepton sector. For certain 4-neutrino mass spectra there exists a direct relation between \meff or the lightest neutrino mass $m_1$ and the neutrino mass measured in $^3$H $β-$decay, $m_{ν_e}$, and the measurement of $\meff \gtap 0.01$ eV and of $m_{ν_e} \gtap 0.4$ eV will give the unique possibility to determine the absolute values of all four neutrino masses and to obtain information on CP-violation in the lepton sector.
Assuming 3-neutrino mixing and massive Majorana neutrinos, we present some implications of the neutrino oscillation solutions of the solar and atmospheric neutrino problems and the results of the CHOOZ experiment for the predictions of the neutrinoless double-beta decay rate. If the present or upcoming searches of neutrinoless double-beta decay give a positive result, the Majorana nature of massive neutrinos will be established. From the determination of the value of the effective Majorana mass, it would be possible to obtain information on the neutrino mass spectrum. With additional information on the absolute value of neutrino masses, it might be possible to infer if CP-parity is violated in the lepton sector.
The general status of neutrino physics are given. The history of the neutrino, starting from Pauli and Fermi, is presented. The phenomenological V-A theory of the weak interaction and the unified theory of the weak and electromagnetic interactions, the so-called Standard Model, are discussed. The problems of of neutrino masses, neutrino mixing, and neutrino oscillations are discussed in some details.
In this short review we discuss the notion of lepton numbers. The strong evidence in favor of neutrino oscillations obtained recently in the Super-Kamiokande atmospheric neutrino experiment and in solar neutrino experiments imply that the law of conservation of family lepton numbers L_e, L_mu and L_tau is strongly violated. We consider the states of flavor neutrinos nu_e, nu_mu and nu_tau and we discuss the evolution of these states in space and time in the case of non-conservation of family lepton numbers due to the mixing of light neutrinos. We discuss and compare different flavor neutrino discovery experiments. We stress that experiments on the search for nu_mu->nu_tau and nu_e->nu_tau oscillations demonstrated that the flavor neutrino nu_tau is a new type of neutrino, different from nu_e and nu_mu. In the case of neutrino mixing, the lepton number (only one) is connected with the nature of massive neutrinos. Such conserved lepton number exist if massive neutrinos are Dirac particles. We review possibilities to check in future experiments whether the conserved lepton number exists.
The problem of the magnitude of the S--factor of the hep process $p + {^3\mathrm{He}} \to {^4\mathrm{He}} + e^+ + ν_e$ is one of the most important unsolved problems in nuclear astrophysics. The magnitude of $S(hep)$ has also an important impact on the interpretation of the Super-Kamiokande solar neutrino results in terms of neutrino oscillations. We point out the possiblity to determine the major hadronic contribution to $S(hep)$ from the measurement of the total cross section of the process $n + {^3\mathrm{H}} \to {^4\mathrm{He}} + e^- + \barν_e$ in experiments with high intensity beams of thermal or cold neutrons.
The present status of the problem of neutrino mass, mixing and neutrino oscillations is briefly summarized. The evidence for oscillations of atmospheric neutrinos found recently in the Super-Kamiokande experiment is discussed. Indications in favor of neutrino oscillations obtained in solar neutrino experiments and in the accelerator LSND experiment are also considered. Implications of existing neutrino oscillation data for neutrino masses and mixing are discussed.
We discuss the problem of solar hep neutrinos originating from the reaction p + 3He -> 4He + e+ + nu and obtain a relation between the astrophysical S-factor of the hep process and the cross section of the process e- + 4He -> 3H + n + nu near threshold. The relation is based on the isotopic invariance of strong interactions. The measurement of the latter cross section would allow to obtain experimental information on S(hep), the value of which, at the moment, is known only from theoretical calculations.
These are lectures given at the CERN-JINR school on high energy physics. The possibilities of the mixing of massive Dirac and Majorana neutrinos are discussed. The theory of neutrino oscillations in vacuum is presented. The trasitions between differen flavor neutrinos in matter are discussed. A short review of the results of the neutrino oscillation experiments is provided.