[en] We consider the oscillations of atmospheric neutrinos in the earth in the three-neutrino scheme with a Δm² hierarchy and a small admixture of the electron neutrino in the heavy mass eigenstate characterized by the mixing angle θ₁₃. We show that for Δm² ≅ (0.5-3) x 10^-3 eV² indicated by the Super-Kamiokande data and sin² 2θ₁₃ < or approx. 0.2, the oscillations of multi-GeV neutrinos in the subdominant ν_μ ↔ ν_e mode are enhanced by the MSW and parametric resonances. The parametric resonance, which occurs when the neutrinos cross the core of the earth, dominated for Δm² ≅ (1-2) x 10^-3 eV², sin² 2θ₁₃ < or approx. 0.06. The resonance matter effects lead to an observable excess of the e-like events with a specific zenith angle dependence even for small θ₁₃. The up-down asymmetry of the multi GeV e-like events can reach 15% for vertical-bar cosΘ_e vertical-bar > 0.2 and up to 30% for vertical-bar cosΘ_e vertical-bar > 0.6, where Θ_e is the zenith angle of the electron. The resonance matter effects are relevant for the interpretation of the Super-Kamiokande data. (author)

[en] We consider the ''standard'' spectrum of the active neutrinos (characterized by strong mass hierarchy and small mixing) with additional sterile, υ_s. The sterile neutrino mixes strongly with the muon neutrino, so that υ_μ ↔ υ_s oscillations solve the atmospheric neutrino problem. We show that the parametric enhancement of the υ_μ ↔ υ_s oscillations occurs for the high energy atmospheric neutrinos which cross the core of the Earth. This can be relevant for the anomaly observed by the MACRO experiment. Solar neutrinos are converted both to υ_μ and υ_s. The heaviest neutrino (approx. υ_τ) may compose the hot dark matter of the Universe. Phenomenology of this scenario is elaborated and crucial experimental signatures are identified. We also discuss properties of the underlying neutrino mass matrix. (author)

[en] Preparations are currently being made at Brookhaven for an experiment to measure the muon anomalous magnetic moment with an accuracy of 3x10^-10. Meanwhile, it is well known that the coefficients of the quantum electrodynamical expansion of the muon anomalous magnetic moment in powers of α are large and growing, so that an estimate of the contributions of thenth order (in e) is of theoretical interest. The first attempt to do this was made previously. Here the author calculates the effect of a set of graphs which was left out of the previous calculations. 5 refs., 4 figs

[en] The NMC measurements of the proton and deuteron structure functions for 0.006 < x < 0.6 and 0.5 < Q² < 55 GeV² and of the neutron-to-proton structure function ratio down to x = 0.0008 are presented. The data agree very well with the earlier results of the BCDMS, SLAC (reanalysed) and EMC NA28 experiments, but disagree with the reanalysed results of the EMC NA2. A parametrization of the low-x structure function F₂, incorporating vector meson dominance dynamics and the QCD-improved parton model, valid at arbitrary Q² and reproducing well the data, is also presented. (Author)

[en] The characteristics of the G-party forbidden τ → νπη decay are calculated in the phenomenological quark model with allowance for isospin-symmetry violation. Contributions of vector and scalar intermediate states to the decay width are studied. The investigated mechanism is a background for searching for second-class currents in the decay τ → νπη. The background should be about 200 τ → νπη decays per year at the cτ-factory intensities. 10 refs., 2 tabs

[en] Core-collapse supernovae emit of order 10⁵⁸ neutrinos and antineutrinos of all flavors over several seconds, with average energies of 10-25 MeV. In the Sudbury Neutrino Observatory (SNO), a future Galactic supernova at a distance of 10 kpc would cause several hundred events. The v_μ and v_τ neutrinos and antineutrinos are of particular interest, as a test of the supernova mechanism. In addition, it is possible to measure or limit their masses by their delay (determined from neutral-current events) relative to the v_e neutrinos (determined from charged current events). Numerical results are presented for such a future supernova as senn in SNO. Under reasonable assumptions, and in the presence of the expected counting statistics, a v_μ or v_τ mass down to about 30 eV can be simply and robustly determined. This seems to be the best technique for direct measurement of these masses. (Author)

[en] The measurements to date of solar neutrino fluxes by the Homestake, Kamiokande, SAGE, and Gallex experiments have provided results which confirm the existence of neutrino fluxes from the pp reactions and the decay of ⁸B in the sun, but leave open the question of whether solar neutrinos undergo flavor change before reaching the earth. This paper will focus on projects that can address this issue which are funded and under construction (Sudbury Neutrino Observatory, Superkamiokande) or in the large prototype stage (ICARUS, Borexino). The remainder if this paper will consist of a short discussion of the physics questions to be addressed by these solar neutrino detectors, followed by descriptions of the four projects likely to be taking data within the next few years. 11 refs., 2 figs

[en] An artificial neutral network was built to select events in the τ→ρυ_τ polarization analysis at LEP/L3, much better selection efficiency has been achieved. Detailed studies show that no systematic errors or bias have been introduced by the application of neural network. A polarization of P_τ = -0.129 +- 0.050 +- 0.050 for this channel was obtained by using a sample of 8977 τ⁺τ^- pairs collected near the peak of Z⁰ resonance. The neural network training method and some details are described

[en] The neutrino long wavelength (just-so) oscillation is reexamined as a solution to the solar neutrino problem. We consider the just-so scenario in various cases: in the framework of the solar models with a relaxed prediction of the boron neutrino flux, as well as in the presence of the nonstandard weak range interactions between neutrino and matter constituents. We show that the fit of the experimental data in the just-so scenario is not very good for any reasonable value of the ⁸B neutrino flux, but it substantially improves if the nonstandard τ-neutrino--electron interaction is included. These new interactions could also remove the conflict of the just-so picture with the shape of the SN 1987A neutrino spectrum. Special attention is devoted to the potential of the future real-time solar neutrino detectors such as Super-Kamiokande, SNO, and BOREXINO, which could provide the model-independent tests for the just-so scenario. In particular, these imply a specific deformation of the original solar neutrino energy spectra and time variation of the intermediate energy monochromatic neutrino (⁷Be and pep) signals

[en] The effects of the composition of matter and magnetic fields on the transitions between active and sterile neutrinos outside the core of a collapsing star are studied. We also consider the possibility that the direction of the magnetic strength lines in the plane transverse to the neutrino momentum may not be fixed (i.e., the field twists). We point out that even a relatively small field twist may give rise to a change in the parameter range of sterile neutrino mixings. The consequences of these changes on neutrino spectrums are discussed