3,122 research outputs found
Solar Neutrinos
The study of solar neutrinos has given since ever a fundamental contribution
both to astroparticle and to elementary particle physics, offering an ideal
test of solar models and offering at the same time relevant indications on the
fundamental interactions among particles. After reviewing the striking results
of the last two decades, which were determinant to solve the long standing
solar neutrino puzzle and refine the Standard Solar Model, we focus our
attention on the more recent results in this field and on the experiments
presently running or planned for the near future. The main focus at the moment
is to improve the knowledge of the mass and mixing pattern and especially to
study in detail the lowest energy part of the spectrum, which represents most
of solar neutrino spectrum but is still a partially unexplored realm. We
discuss this research project and the way in which present and future
experiments could contribute to make the theoretical framemork more complete
and stable, understanding the origin of some "anomalies" that seem to emerge
from the data and contributing to answer some present questions, like the exact
mechanism of the vacuum to matter transition and the solution of the so called
solar metallicity problem.Comment: 51 pages, to be published in Special Issue on Neutrino Physics,
Advances in High Energy Physics Hindawi Publishing Corporation 201
Global Analysis of Solar Neutrino Oscillations Including SNO CC Measurement
For active and sterile neutrinos, we present the globally allowed solutions
for two neutrino oscillations. We include the SNO CC measurement and all other
relevant solar neutrino and reactor data. Five active neutrino oscillation
solutions (LMA, LOW, SMA, VAC, and Just So2) are currently allowed at 3 sigma;
three sterile neutrino solutions (Just So2, SMA, and VAC) are allowed at 3
sigma. The goodness of fit is satisfactory for all eight solutions. We also
investigate the robustness of the allowed solutions by carrying out global
analyses with and without: 1) imposing solar model constraints on the 8B
neutrino flux, 2) including the Super-Kamiokande spectral energy distribution
and day-night data, 3) including a continuous mixture of active and sterile
neutrinos, 4) using an enhanced CC cross section for deuterium (due to
radiative corrections), and 5) a optimistic, hypothetical reduction by a factor
of three of the error of the SNO CC rate. For every analysis strategy used in
this paper, the most favored solutions all involve large mixing angles: LMA,
LOW, or VAC. The favored solutions are robust, but the presence at 3 sigma of
individual sterile solutions and the active Just So2 solution is sensitive to
the analysis assumptions.Comment: 9 figures, higher resolution versions at http://www.sns.ias.edu/~jnb,
added references and clarification
Solar Neutrinos Before and After Neutrino 2004
We compare, using a three neutrino analysis, the allowed neutrino oscillation
parameters and solar neutrino fluxes determined by the experimental data
available Before and After Neutrino 2004. New data available after Neutrino2004
include refined KamLAND and gallium measurements. We use six different
approaches to analyzing the KamLAND data. We present detailed results using all
the available neutrino and anti-neutrino data for Delta m^2_{12}, tan^2
theta_{12}, sin^2 theta_{13}, and sin^2 eta (sterile fraction). Using the same
complete data sets, we also present Before and After determinations of all the
solar neutrino fluxes, which are treated as free parameters, an upper limit to
the luminosity fraction associated with CNO neutrinos, and the predicted rate
for a 7Be solar neutrino experiment. The 1 sigma (3 sigma) allowed range of
Delta m^2_{21} = (8.2 +- 0.3) (^+1.0_-0.8)times 10^{-5} eV^2 is decreased by a
factor of 1.7 (5), but the allowed ranges of all other neutrino oscillation
parameters and neutrino fluxes are not significantly changed. Maximal mixing is
disfavored at 5.8 sigma and the bound on the mixing angle theta_{13} is
slightly improved to sin^2 theta_{13}<0.048 at 3 sigma. The predicted rate in a
7Be neutrino-electron scattering experiment is (0.665 +-0.015) of the rate
implied by the BP04 solar model in the absence of neutrino oscillations. The
corresponding predictions for p-p and pep experiments are, respectively, 0.707
{+0.011}{-0.013} and 0.644 {+0.011}{-0.013}. We derive upper limits to CPT
violation in the weak sector by comparing reactor anti-neutrino oscillation
parameters with neutrino oscillation parameters. We also show that the recent
data disfavor at 91 % CL a proposed non-standard interaction description of
solar neutrino oscillations.Comment: Added predictions for p-p and pep neutrino-electron scattering rate;
publishe
Updated determination of the solar neutrino fluxes from solar neutrino data
We present an update of the determination of the solar neutrino fluxes from a
global analysis of the solar and terrestrial neutrino data in the framework of
three-neutrino mixing. Using a Bayesian analysis we reconstruct the posterior
probability distribution function for the eight normalization parameters of the
solar neutrino fluxes plus the relevant masses and mixing, with and without
imposing the luminosity constraint. We then use these results to compare the
description provided by different Standard Solar Models. Our results show that,
at present, both models with low and high metallicity can describe the data
with equivalent statistical agreement. We also argue that even with the present
experimental precision the solar neutrino data have the potential to improve
the accuracy of the solar model predictions.Comment: 20 pages, 2 tables, 5 figures. arXiv admin note: substantial text
overlap with arXiv:0910.458
A non-resonant dark-side solution to the solar neutrino problem
We re-analyse spin-flavour precession solutions to the solar neutrino problem
in the light of the recent SNO CC result as well as the 1258--day
Super-Kamiokande data and the upper limit on solar anti-neutrinos. In a
self-consistent magneto-hydrodynamics approach the resulting scheme has only 3
effective parameters: , and the neutrino mixing angle
. We show how a rates-only analysis for fixed slightly
favours spin-flavour precession (SFP) solutions over oscillations (OSC). In
addition to the resonant solution (RSFP for short), there is a new non-resonant
solution (NRSFP) in the ``dark-side''. Both RSFP and NRSFP lead to flat recoil
energy spectra in excellent agreement with the latest SuperKamiokande data. We
also show that in the presence of a neutrino transition magnetic moment of
Bohr magneton, a magnetic field of 80 KGauss eliminates all large
mixing solutions other than the so-called LMA solution.Comment: 12 pages, 3 postscript figures, using elsart.cls. Published versio
What can we learn from neutrinoless double beta decay experiments
We assess how well next generation neutrinoless double beta decay and normal neutrino beta decay experiments can answer four fundamental questions. 1) If neutrinoless double beta decay searches do not detect a signal, and if the spectrum is known to be inverted hierarchy, can we conclude that neutrinos are Dirac particles? 2) If neutrinoless double beta decay searches are negative and a next generation ordinary beta decay experiment detects the neutrino mass scale, can we conclude that neutrinos are Dirac particles? 3) If neutrinoless double beta decay is observed with a large neutrino mass element, what is the total mass in neutrinos? 4) If neutrinoless double beta decay is observed but next generation beta decay searches for a neutrino mass only set a mass upper limit, can we establish whether the mass hierarchy is normal or inverted? We base our answers on the expected performance of next generation neutrinoless double beta decay experiments and on simulations of the accuracy of calculations of nuclear matrix elements
Models of Neutrino Masses and Mixings
We review theoretical ideas, problems and implications of neutrino masses and
mixing angles. We give a general discussion of schemes with three light
neutrinos. Several specific examples are analyzed in some detail, particularly
those that can be embedded into grand unified theories.Comment: 44 pages, 2 figures, version accepted for publication on the Focus
Issue on 'Neutrino Physics' edited by F.Halzen, M.Lindner and A. Suzuki, to
be published in New Journal of Physics
Damping of supernova neutrino transitions in stochastic shock-wave density profiles
Supernova neutrino flavor transitions during the shock wave propagation are
known to encode relevant information not only about the matter density profile
but also about unknown neutrino properties, such as the mass hierarchy (normal
or inverted) and the mixing angle theta_13. While previous studies have
focussed on "deterministic" density profiles, we investigate the effect of
possible stochastic matter density fluctuations in the wake of supernova shock
waves. In particular, we study the impact of small-scale fluctuations on the
electron (anti)neutrino survival probability, and on the observable spectra of
inverse-beta-decay events in future water-Cherenkov detectors. We find that
such fluctuations, even with relatively small amplitudes, can have significant
damping effects on the flavor transition pattern, and can partly erase the
shock-wave imprint on the observable time spectra, especially for
sin^2(theta_13) > O(10^-3).Comment: v2 (23 pages, including 6 eps figures). Typos removed, references
updated, matches the published versio
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