154 research outputs found
Vacuum oscillations of solar neutrinos: correlation between spectrum distortion and seasonal variations
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
We show that a left-handed neutrino can oscillate into its -
conjugated state with maximal amplitude, in direct analogy with
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?
We consider a solution of the atmospheric neutrino problem based on
oscillations of muon neutrinos to sterile neutrinos:
. The zenith angle () 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 and . 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
The see-saw mechanism for neutrino masses based on the Grand Unification
leads to the mass of the heaviest neutrino () in the range
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 which mixes predominantly with muon neutrino through the
mixing mass eV. The introduction of such a singlet allows
one (i) to solve the atmospheric neutrino problem via the 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
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
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 -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 -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
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 -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 and splitting
) the two definitions coincide up to
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 -schemes motivated, in
particular, by the LSND results. In this case the accuracy of the mass
determination turns out to be better than .Comment: 15 pages, Version to appear in Phys. Lett.
RF deflector based on standing wave and π/3 mode
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
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 () transition
channels, neutrino-antineutrino resonant conversion, large amplitude
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
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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