3,680 research outputs found
Majorana Neutrino Masses from Neutrinoless Double Beta Decay and Cosmology
When three Majorana neutrinos describe the solar and atmospheric neutrino
data via oscillations, a nonzero measurement of neutrinoless double beta
() decay can determine the sum of neutrino masses
if the solar solution has small-angle mixing, and place a lower bound on for large-angle solar mixing. If in addition a nonzero is
deduced from cosmology, the neutrino mass spectrum may be uniquely specified
for some ranges of neutrino parameters. For eV, the
small-angle solar solution is excluded by the current upper limit on
neutrinoless double beta decay. In models with maximal solar mixing the
phases of the neutrinos may be strongly constrained by stringent upper bounds
on decay.Comment: 13 pages, Latex2.09, uses epsf.sty, 4 postscript figure
Seasonal and Energy Dependence of Solar Neutrino Vacuum Oscillations
We make a global vacuum neutrino oscillation analysis of solar neutrino data,
including the seasonal and energy dependence of the recent Super-Kamiokande
708-day results. The best fit parameters for \nu_e oscillations to an active
neutrino are \delta m^2 = 4.42\times10^{-10} eV^2, \sin^2 2\theta = 0.93. The
allowed mixing angle region is consistent with bi-maximal mixing of three
neutrinos. Oscillations to a sterile neutrino are disfavored. Allowing an
enhanced hep neutrino flux does not significantly alter the oscillation
parameters.Comment: Latex2.09, 10 pages, uses epsf.sty, 3 postscript figure
Testing the LMA solution with solar neutrinos independently of solar models
We perform a comparative study of two methods of determining the survival
probabilities of low, intermediate, and high energy solar neutrinos that
emphasizes the general agreement between the Large Mixing Angle (LMA) solution
and extant solar neutrino data. The first analysis is oscillation
parameter-independent and the second analysis involves an approximate
calculation of the survival probabilities in the three energy ranges that
depends only on oscillation parameters. We show that future experiments like
BOREXino, CLEAN, Heron, LENS and MOON, that measure and Be neutrinos,
will facilitate a stringent test of the LMA solution independently of the
Standard Solar Model (SSM), without recourse to earth-matter effects.
Throughout, we describe the role of SSM assumptions on our results. If the LMA
solution passes the test without needing to be modified, it may be possible to
establish that is nonzero at more than assuming the SSM
prediction for the flux is correct.Comment: Final SNO salt-phase data included in analysis. Version to appear in
PL
Piecing the Solar Neutrino Puzzle Together at SNO
We perform an oscillation parameter-independent analysis of solar neutrino
flux measurements from which we predict the charged-current rate at SNO
relative to Standard Solar Model to be for oscillations to active (sterile) neutrinos. By
alternately considering the B flux normalization fixed and free, we find
that the flux measured by Super-Kamiokande (SK) not being a result of
oscillations is strongly disfavored for oscillations to active neutrinos. SNO
will determine the best-fit value of the B flux normalization
(equal to the neutral-current rate), without recourse to neutral-current
measurements, from the derived relation . Using a simple parameterization of the fraction of high,
intermediate, and low energy solar neutrinos starting above resonance, we
reproduce the results of global analyses to good accuracy; we find that the LMA
solution with a normal mass hierarchy is clearly favored. With free,
our analysis for oscillations to active neutrinos gives
, which corresponds to .Comment: Version to appear in PL
How two neutrino superbeam experiments do better than one
We examine the use of two superbeam neutrino oscillation experiments with
baselines \lsim 1000 km to resolve parameter degeneracies inherent in the
three-neutrino analysis of such experiments. We find that with appropriate
choices of neutrino energies and baselines two experiments with different
baselines can provide a much better determination of the neutrino mass ordering
than a single experiment alone. Two baselines are especially beneficial when
the mass scale for solar neutrino oscillations is \gsim
5\times10^{-5} eV. We also examine CP violation sensitivity and the
resolution of other parameter degeneracies. We find that the combined data of
superbeam experiments with baselines of 295 and 900 km can provide sensitivity
to both the neutrino mass ordering and CP violation for
down to 0.03 for eV. It
would be highly advantageous to have a 10% determination of before the beam energies and baselines are finalized, although if
is not that well known, the neutrino energies and
baselines can be chosen to give fairly good sensitivity for a range of .Comment: 18 pages, 6 PS figures, added references and revised discussio
Neutrino Mass Matrices in Models with Horizontal Symmetries
We have studied the most general neutrino mass matrices in models with SU(2)
and SU(3) horizontal symmetries. Without going into the details of the models
it is possible to write down the effective operators, which predict the
structure of the Majorana neutrino mass matrices. Unlike other extensions of
the standard model, the structure is now independent of the effective Yukawa
couplings and depends entirely on the Higgs which gives mass to the other
fermions. In the case of SU(3) symmetries the lowest dimensional operators are
forbidden requiring a low mass scale for lepton number violation.Comment: 11 pages latex file, a few references added in 2nd versio
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