154 research outputs found

    Vacuum oscillations of solar neutrinos: correlation between spectrum distortion and seasonal variations

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    Long length vacuum oscillations solution of the solar neutrino problem is discussed. We show that there is a strict correlation between a distortion of the neutrino energy spectrum and an amplitude of seasonal variations of the neutrino flux. The slope parameter which characterizes a distortion of the recoil electron energy spectrum in the Super-Kamiokande experiment and the seasonal asymmetry of the signal have been calculated in a wide range of oscillation parameters. The correlation of the slope and asymmetry gives crucial criteria for identification or exclusion of this solution. For the positive slope indicated by preliminary Super-Kamiokande data we predict (40 - 60) % enhancement of the seasonal variations.Comment: 11 pages, 4 eps figures, LaTeX, analytical study and some explanations added, updated experimental results use

    Pontecorvo's Original Oscillations Revisited

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    We show that a left-handed neutrino νL\nu_L can oscillate into its CPCP- conjugated state νˉR\bar{\nu}_R with maximal amplitude, in direct analogy with K0Kˉ0K^0-\bar{K}^0 oscillations. Peculiarities of such oscillations under different conditions are studied.Comment: LaTeX, 14 pages, 1 figure (not included but available upon request by fax or ordinary mail), SISSA 9/93/EP, IC/93/1

    Parametric Resonance in Oscillations of Atmospheric Neutrinos?

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    We consider a solution of the atmospheric neutrino problem based on oscillations of muon neutrinos to sterile neutrinos: νμ\nu_{\mu} \leftrightarrow νs\nu_s. The zenith angle (Θ\Theta) dependences of the neutrino and upward-going muon fluxes in presence of these oscillations are studied. The dependences have characteristic form with two dips: at cosΘ=0.6÷0.2\cos \Theta = -0.6 \div -0.2 and cosΘ=1.0÷0.8\cos \Theta = -1.0 \div -0.8. The latter dip is due to parametric resonance in oscillations of neutrinos which cross the core of the earth. A comparison of predictions with data from the MACRO, Baksan and Super-Kamiokande experiments is given.Comment: 14 pages + 9 eps figures in 6 pages, Latex fil

    Rescuing Grand Unification Scenario for Neutrino Mass

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    The see-saw mechanism for neutrino masses based on the Grand Unification leads to the mass of the heaviest neutrino (ντ\approx \nu_{\tau}) in the range (23)103(2 - 3)\cdot 10^{-3} eV and hence to a solution of the solar neutrino problem through the \nu_e-\nu_\t conversion. We suggest the existence of a light singlet fermion SS which mixes predominantly with muon neutrino through the mixing mass mμsO(1)m_{\mu s} \sim O(1) eV. The introduction of such a singlet allows one (i) to solve the atmospheric neutrino problem via the νμS\nu_{\mu} \leftrightarrow S oscillations, (ii) to explain the LSND result and (iii) to get two component hot dark matter in the Universe. The phenomenology of this scenario is considered and the origin of the singlet as well as of the scale m_{\m s} is discussed.Comment: LaTex, 16 pages including one figur

    Neutrino mass spectrum and lepton mixing

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    The program of reconstruction of the neutrino mass and flavor spectrum is outlined and the present status of research is summarized. We describe the role of future solar and atmospheric neutrino experiments, detection of the Galactic supernovae and double beta decay searches in accomplishing this program. The LSND result and four neutrino mass spectra are considered in connection with recent searches for the sterile components in the solar and atmospheric neutrino fluxes.Comment: 8 pages, latex, 4 figures. Talk given at the XIX International Conference on Neutrino Physics and Astrophysics, Neutrino-2000, Sudbury, Canada, 16 - 21 June 200

    Towards the Solution of the Solar Neutrino Problem

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    We discuss various aspects of the solar neutrino spectrum distortion and time variations of fluxes. (i) Oscillations of neutrinos which cross the mantle and the core of the Earth can be parametrically enhanced. The parametric effect gives correct physical interpretation of the calculated day-night asymmetry. (ii) Solution of the ν\nu_{\odot}-problem in schemes with three and more neutrinos which accommodate explanations of other neutrino anomalies, in particular, the atmospheric neutrino anomaly, can lead to complicated distortion of the boron neutrino spectrum. (iii) The study of correlations between time (seasonal or day-night) variations and spectrum distortion will help to identify the solution of the ν\nu_{\odot}-problem.Comment: 10 pages, LaTeX, 9 figures. Invited talk presented at the Neutrino-98 conference, Takayama, Japan, June 1998. Several typos and eps file of fig.5 corrected; reference adde

    On the Effective Mass of the Electron Neutrino in Beta Decay

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    In the presence of mixing between massive neutrino states, the distortion of the electron spectrum in beta decay is, in general, a function of several masses and mixing angles. For 3ν3\nu-schemes which describe the solar and atmospheric neutrino data, this distortion can be described by a single effective mass, under certain conditions. In the literature, two different definitions for the effective mass have been suggested. We show that for quasi-degenerate mass schemes (with an overall mass scale mm and splitting Δm2\Delta m^2) the two definitions coincide up to (Δm2)2/m4(\Delta m^2)^2/m^4 corrections. We consider the impact of different effective masses on the integral energy spectrum. We show that the spectrum with a single mass can be used also to fit the data in the case of 4ν4\nu-schemes motivated, in particular, by the LSND results. In this case the accuracy of the mass determination turns out to be better than (1015)(10 - 15)%.Comment: 15 pages, Version to appear in Phys. Lett.

    RF deflector based on standing wave and π/3 mode

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    For accelerating beam characteristics measurement together with travelling wave RF deflectors with Е11 wave type, SW deflectors with π mode are used. The disadvantage of TW deflectors is the small frequency division between working and neighboring modes. SW heterogeneous structure with DLS type is proposed. The working mode is π/3.Для метрики характеристик прискореного пучка поряд з високочастотними дефлекторами (ВЧД) на хвилі Е11 в режимі бігучої хвилі використовуються і ВЧД, що працюють у режимі стоячої хвилі на виді коливань π. Недоліком їх є поганий частотний поділ робочого виду коливань з сусідніми видами. Запропоновано неоднорідну структуру у вигляді круглого диафрагмованого хвилеводу на стоячій хвилі і виді коливань π/3.Для метрики характеристик ускоренного пучка наряду с высокочастотными дефлекторами (ВЧД) на волне Е11 в режиме бегущей волны используются и ВЧД, работающие в режиме стоячей волны на виде колебаний π. Недостатком их является плохое частотное разделение рабочего вида колебаний с соседними видами. Предложена неоднородная структура в виде круглого диафрагмированного волновода на стоячей волне и виде колебаний π/3

    Neutrinos with Mixing in Twisting Magnetic Fields

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    Transitions in a system of neutrinos with vacuum mixing and magnetic moments, propagating in matter and transverse magnetic field, are considered. It is shown that in the realistic case of magnetic field direction varying along the neutrino path qualitatively new phenomena become possible: permutation of neutrino conversion resonances, appearance of resonances in the neutrino-antineutrino (νlLνˉlR\nu_{lL}\leftrightarrow\bar{\nu}_{lR}) transition channels, neutrino-antineutrino resonant conversion, large amplitude νlLνˉlR\nu_{lL}\leftrightarrow\bar{\nu}_{lR} oscillations, merging of different resonances (triple resonances). Possible phenomenological implications of these effects are briefly discussed.Comment: LaTeX, 35 pages, 4 figures (not included but available upon request). In memoriam of Ya.A. Smorodinsky. SISSA-170/92/E

    Electron Spin Relaxation in a Semiconductor Quantum Well

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    A fully microscopic theory of electron spin relaxation by the D'yakonov-Perel' type spin-orbit coupling is developed for a semiconductor quantum well with a magnetic field applied in the growth direction of the well. We derive the Bloch equations for an electron spin in the well and define microscopic expressions for the spin relaxation times. The dependencies of the electron spin relaxation rate on the lowest quantum well subband energy, magnetic field and temperature are analyzed.Comment: Revised version as will appear in Physical Review
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