785 research outputs found
Precise Formulation of Neutrino Oscillation in the Earth
We give a perturbation theory of neutrino oscillation in the Earth. The
perturbation theory is valid for neutrinos with energy E \gsim 0.5 GeV. It is
formulated using trajectory dependent average potential. Non-adiabatic
contributions are included as the first order effects in the perturbation
theory. We analyze neutrino oscillation with standard matter effect and with
non-standard matter effect. In a three flavor analysis we show that the
perturbation theory gives a precise description of neutrino conversion in the
Earth. Effect of the Earth matter is substantially simplified in this
formulation.Comment: References added, 21 pages, 10 figures, version to appear in PR
Solar neutrinos and 1-3 leptonic mixing
Effects of the 1-3 leptonic mixing on the solar neutrino observables are
studied and the signatures of non-zero are identified. For this
we have re-derived the formula for -survival probability including all
relevant corrections and constructed the iso-contours of observables in the
plane. Analysis of the solar neutrino
data gives (90% C.L.) for
eV. The combination of the ratio CC/NC at
SNO and gallium production rate selects
(). The global fit of all oscillation data leads to zero best value of
. The sensitivity ( error) of future solar
neutrino studies to can be improved down to 0.01 - 0.02 by
precise measurements of the pp-neutrino flux and the CC/NC ratio as well as
spectrum distortion at high ( MeV) energies. Combination of experimental
results sensitive to the low and high energy parts of the solar neutrino
spectrum resolves the degeneracy of angles and .
Comparison of as well as measured in
the solar neutrinos and in the reactor/accelerator experiments may reveal new
effects which can not be seen otherwise.Comment: 36 pages, latex, 10 figures. Analysis and figures are updated with
new (salt phase II) SNO results, several clarifications added, typos
correcte
Density profiles of supernova matter and determination of neutrino parameters
The flavor conversion of supernova neutrinos can lead to observable
signatures related to the unknown neutrino parameters. As one of the
determinants in dictating the efficiency of resonant flavor conversion, the
local density profile near the MSW resonance in a supernova environment is,
however, not so well understood. In this analysis, variable power-law functions
are adopted to represent the independent local density profiles near the
locations of resonance. It is shown that the uncertain matter density profile
in a supernova, the possible neutrino mass hierarchies, and the undetermined
1-3 mixing angle would result in six distinct scenarios in terms of the
survival probabilities of and . The feasibility of
probing the undetermined neutrino mass hierarchy and the 1-3 mixing angle with
the supernova neutrinos is then examined using several proposed experimental
observables. Given the incomplete knowledge of the supernova matter profile,
the analysis is further expanded to incorporate the Earth matter effect. The
possible impact due to the choice of models, which differ in the average energy
and in the luminosity of neutrinos, is also addressed in the analysis.Comment: 27 pages, 10 figures. text and figures revised, references added, to
appear in Phys. Rev.
Random magnetic fields inducing solar neutrino spin-flavor precession in a three generation context
We study the effect of random magnetic fields in the spin-flavor precession
of solar neutrinos in a three generation context, when a non-vanishing
transition magnetic moment is assumed. While this kind of precession is
strongly constrained when the magnetic moment involves the first family, such
constraints do not apply if we suppose a transition magnetic moment between the
second and third families. In this scenario we can have a large non-electron
anti-neutrino flux arriving on Earth, which can lead to some interesting
phenomenological consequences, as, for instance, the suppression of day-night
asymmetry. We have analyzed the high energy solar neutrino data and the KamLAND
experiment to constrain the solar mixing angle, and solar mass difference, and
we have found a larger shift of allowed values.Comment: 10 pages, 3 figure
Bilarge neutrino mixing from supersymmetry with high-scale nonrenormalizable interactions
We suggest a supersymmetric (SUSY) explanation of neutrino masses and mixing,
where nonrenormalizable interactions in the hidden sector generate lepton
number violating Majorana mass terms for both right-chiral sneutrinos and
neutrinos. It is found necessary to start with a superpotential including an
array of gauge singlet chiral superfields. This leads to nondiagonal mass terms and almost diagonal SUSY breaking -terms. As a result, the
observed pattern of bilarge mixing can be naturally explained by the
simultaneous existence of the seesaw mechanism and radiatively induced masses.
Allowed ranges of parameters in the gauge singlet sector are delineated,
corresponding to each of the cases of normal hierarchy, inverted hierarchy and
degenerate neutrinos.Comment: 19 pages, 5 figures. Minor modifications are made in the title and
the text, some new references are added. To appear in this form in Physical
Review
Solar neutrino spectrum, sterile neutrinos and additional radiation in the Universe
Recent results from the SNO, Super-Kamiokande and Borexino experiments do not
show the expected upturn of the energy spectrum of events (the ratio ) at low energies. At the same time, cosmological observations
testify for possible existence of additional relativistic degrees of freedom in
the early Universe: . These facts strengthen the case
of very light sterile neutrino, , with eV, which mixes weakly with the active neutrinos. The
mixing in the mass eigenstate characterized by can explain an absence of the upturn. The mixing of in
the eigenstate with leads to production of
via oscillations in the Universe and to additional contribution before the big bang nucleosynthesis and later. Such a
mixing can be tested in forthcoming experiments with the atmospheric neutrinos
as well as in future accelerator long baseline experiments. It has substantial
impact on conversion of the supernova neutrinos.Comment: 27 pages, LaTeX, 14 eps figures, 3 figures and additional
considerations adde
On in situ Determination of Earth Matter Density in Neutrino Factory
We point out that an accurate in situ determination of the earth matter
density \rho is possible in neutrino factory by placing a detector at the magic
baseline, L = \sqrt{2} \pi / G_{F} N_{e} where N_{e} denotes electron number
density. The accuracy of matter density determination is excellent in a region
of relatively large theta_{13} with fractional uncertainty \delta \rho / \rho
of about 0.43%, 1.3%, and \lsim 3% at 1 sigma CL at sin^2 2theta_{13}=0.1,
10^{-2}, and 3 x 10^{-3}, respectively. At smaller theta_{13} the uncertainty
depends upon the CP phase delta, but it remains small, 3%-7% in more than 3/4
of the entire region of delta at sin^2 2theta_{13} = 10^{-4}. The results would
allow us to solve the problem of obscured CP violation due to the uncertainty
of earth matter density in a wide range of theta_{13} and delta. It may provide
a test for the geophysical model of the earth, or it may serve as a method for
stringent test of the MSW theory of neutrino propagation in matter once an
accurate geophysical estimation of the matter density is available.Comment: 21 pages, 4 figures, version to appear in PR
Testing CPT Symmetry with Supernova Neutrinos
Diagnosing core of supernova requires favor-dependent reconstruction of three
species of neutrino spectra, \nu_e, \bar{\nu}_{e} and \nu_x (a collective
notation for \nu_{\mu}, \bar{\nu}_{\mu}, \nu_{\tau}, and \bar{\nu}_{\tau}). We
point out that, assuming the information available, CPT symmetry can be tested
with supernova neutrinos. We classify all possible level crossing patterns of
neutrinos and antineutrinos into six cases and show that half of them contains
only the CPT violating mass and mixing patterns. We discuss how additional
informations from terrestrial experiments help identifying CPT violation by
narrowing down the possible flux patterns. Although the method may not be good
at precision test, it is particularly suited to uncover gross violation of CPT
such as different mass patterns of neutrinos and antineutrinos. The power of
the method is due to the nature of level crossing in supernova which results in
the sensitivity to neutrino mass hierarchy and to the unique characteristics of
in situ preparation of both \nu and \bar{\nu} beams. Implications of our
discussion to the conventional analyses with CPT conservation are also briefly
mentioned.Comment: 24 pages, 4 figures, discussion added on narrowing down flux patterns
by terrestrial measuremen
Supernova bound on keV-mass sterile neutrinos reexamined
Active-sterile neutrino mixing is strongly constrained for m_s > 100 keV to
avoid excessive energy losses from supernova cores. For smaller m_s, matter
effects suppress the effective mixing angle except for a resonant range of
energies where it is enhanced. We study the case of \nu_tau-\nu_s-mixing where
a \nu_tau-\bar\nu_tau asymmetry builds up due to the strong excess of \nu_s
over \bar\nu_s emission or vice versa, reducing the overall emission rate. In
the warm dark matter range m_s < 10 keV the mixing angle is essentially
unconstrained.Comment: 6 pages, 4 figures; minor changes, references updated, matches the
published versio
Construction and analysis of a simplified many-body neutrino model
In dense neutrino systems, such as found in the early Universe, or near a
supernova core, neutrino flavor evolution is affected by coherent
neutrino-neutrino scattering. It has been recently suggested that many-particle
quantum entanglement effects may play an essential role in these systems,
potentially invalidating the traditional description in terms of a set of
single-particle evolution equations. We model the neutrino system by a system
of interacting spins, following an earlier work which showed that such a spin
system can in some cases be solved exactly. We extend this work by constructing
an exact analytical solution to a more general spin system, including initial
states with asymmetric spin distribution and, moreover, not necessarily aligned
along the same axis. Our solution exhibits a rich set of behaviors, including
coherent oscillations and dephasing and a transition from the classical to
quantum regimes. We argue that the classical evolution of the spin system
captures the entire coherent behavior of the neutrino system, while the quantum
effects in the spin system capture some, but not all, of the neutrino
incoherent evolution. By comparing the spin and neutrino systems, we find no
evidence for the violation of the accepted one-body description, though the
argument involves some subtleties not appreciated before. The analysis in this
paper may apply to other two-state systems beyond the neutrino field.Comment: 22 pages, 7 figure
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