The MSW mechanism for three neutrino generations and the solar neutrino puzzle

We analyse the ³⁷Cl experiment for three neutrino generations with arbitrary mixing angles in the adiabatic approximation and present the resulting ⁸B-neutrino energy spectrum.     

Limits on the neutrino magnetic moment from solar neutrino experiments

If neutrinos have non-vanishing mass and non-vanishing magnetic moments, then electron neutrinos emitted in nuclear reactions in the solar interior may undergo flavour oscillations, spin precession or resonant spin-flavour precession. Assuming equal values for the magnetic moments of all neutrino flavours and using the data from Homestake and SuperKamiokande we obtain an upper limit on the neutrino magnetic moment and find μ_νe ≤ (2.2 − 2.3) × 10⁻¹⁰μ_B, within four standard solar models. We also point out that this limit may be further reduced if the detector threshold energy for the ν_e,χe⁻ scattering is decreased.     

Supernova neutrino energy spectra and the MSW effect

The distortions in the thermal energy spectra for neutrinos produced in a supernova when a resonant oscillation, MSW effect, occurs are determined. In order to show this effect for some relevant and representative examples of unified gauge models, we have chosen SO(10), and SU(5)_SUSY, SO(10)_SUSY with a particular scheme for fermion masses (DHR model). The analysis has been performed for two choices of neutrinos parameters, predicted by the above models, and capable to explain the solar neutrino problem. In both cases one observes a strong distortion in the electron neutrino energy spectrum. This effect, computed for a wide range of SO(10)_SUSY models has produced the same results of the previous supersymmetric ones.     

The effect of random matter density perturbations on the MSW solution to the solar neutrino problem

We consider the implications of solar matter density random noise upon resonant neutrino conversion. The evolution equation describing MSW-like conversion is derived in the framework of the Schrödinger approach. We study quantitatively the effect of such matter perturbations upon both large and small mixing angle MSW solutions to the solar neutrino problem. This is carried out both for the active-active v_e → v_μ,τ as well as active-sterile v_e → v_s conversion channels. We find that the small mixing MSW solution is much more stable (especially in Δm² than the large mixing solution. The possible existence of solar matter density noise at the few percent level could be tested at future solar neutrino experiments, especially Borexino.     

Sterile neutrinos and future solar neutrino experiments

It is shown that future solar neutrino experiments (SNO, Super-Kamiokande and others), in which high energy neutrinos will be detected (mostly from ⁸B decay), may allow to answer in a model independent way the question whether there are transitions of solar v_e's into sterile states. No assumptions about the initial flux of ⁸B neutrinos are made. Lower bounds for the probability of transition of solar v_e's into all sterile states are derived and expressed through measurable quantities.     

Testing the vacuum oscillation and the MSW solutions of the solar neutrino problem

Solar model independent tests of the vacuum oscillation and MSW solutions of the solar neutrino problem are considered. Detailed predictions for time (seasonal) variations of the signals due to neutrino oscillations in vacuum are given for the future solar neutrino detectors (SNO, Super-Kamiokande, BOREXINO, HELLAZ). Results on the distortions of the spectra of ⁸B neutrinos, and of e⁻ from the reaction ν + e⁻ → ν + e⁻ induced by ⁸B neutrinos, are presented in the cases of vacuum oscillations or MSW transitions for a large number of values of the relevant parameters. The possibilities to distinguish between the vacuum oscillation, the MSW adiabatic, and the MSW nonadiabatic transitions in the future solar neutrino experiments are discussed.     

Linking solar and long baseline terrestrial neutrino experiments

We show that, in the framework of three light neutrino species with hierarchical masses and assuming no fine tuning between the entries of the neutrino mass matrix, one can use the solar neutrino data to obtain information on the element U(e3) of the lepton mixing matrix. Conversely, a measurement of U(e3) in atmospheric or long baseline accelerator or reactor neutrino experiments would help discriminate between possible oscillation solutions of the solar neutrino problem.     

On the presence of fictitious solar neutrino flux variations in radiochemical experiments

Journal of Experimental and Theoretical Physics - The currently available data on solar neutrino flux variation in radiochemical experiments and Cherenkov measurements have so far defied a simple...     

Statistical analysis of solar neutrino data

We calculate with Monte Carlo the goodness of fit and the confidence level of the standard allowed regions for the neutrino oscillation parameters obtained from the fit of the total rates measured in solar neutrino experiments. We show that they are significantly overestimated in the standard method. We also calculate exact allowed regions with correct frequentist coverage. We show that the exact VO, LMA and LOW regions are much larger than the standard ones and merge together giving an allowed band at large mixing angles for all Δm² 10⁻¹⁰ eV².     

Matter effect in neutrino oscillations for long-baseline experiments

This paper is devoted to the matter effect and its role in Long-Baseline experiments. As examples, the NOvA and DUNE experiments will be discussed.     

The sun as a nonlinear thermodynamic system: the solar neutrino experiments

The nonlinear constructive law between the collision friction force and the corresponding momentum flux in solar plasma is investigated. A new coherent steady state of the plasma is found in addition to the disordered steady state. The latter is worked out and compared with the solar neutrino experiments to show that the sun may assume a coherent state.     

Contribution of gallium experiments to the understanding of solar physics and neutrino physics

The results of gallium measurements of solar neutrino and measurements with artificial sources of neutrinos are presented. Conclusions are drawn from these results, and the potential of the SAGE experiment for studying transitions of active neutrinos to sterile states for Δm ² > 0.5 eV² and a sensitivity of a few percent to the disappearance of electron neutrinos is examined.