184 research outputs found
Effects of non-standard neutrino interactions on MSW-LMA solution to the solar neutrino problem
We show that the non-standard neutrino interactions can play a role as
sub-leading effect on the solar neutrino oscillations. We observe that very
small flavor universality violations of order of 0.1-0.2 G_F is sufficient to
induce two phenomena: suppression of the eletronic neutrino earth regeneration
and a shift of the resonance layer in the sun. We obtain these phenomena even
in the absence of any flavor changing interactions. We discuss their
consequences and confront with a global analysis of solar+KamLAND results. We
conclude that a new compatibility region in the Delta m^2 x tan^2\theta, which
we call very low Large Mixing Angle region, is found for Delta m^2 ~ 1e-5 eV^2
and tan^2\theta= 0.45.Comment: references added, small changes in text, some changes in predictions
of KamLAND future sensitivity to NSNI parameter
Short-Baseline Neutrino Oscillations at a Neutrino Factory
Within the framework of three-neutrino and four-neutrino scenarios that can
describe the results of the LSND experiment, we consider the capabilities of
short baseline neutrino oscillation experiments at a neutrino factory. We find
that, when short baseline (L \alt 100 km) neutrino factory measurements are
used together with other accelerator-based oscillation results, the complete
three-neutrino parameter space can best be determined by measuring the rate of
oscillations, and measuring CP violation with either
or oscillations (including the
corresponding antineutrino channels). With measurements of CP violation in both
and it may be possible to
distinguish between the three- and four-neutrino cases.Comment: 16 pages, Revtex (single-spaced), 8 postscript figures, uses epsf.st
Status of a hybrid three-neutrino interpretation of neutrino data
We reanalyze the non-standard interaction (NSI) solutions to the solar
neutrino problem in the light of the latest solar, atmospheric and reactor
neutrino data. We show that such solutions, although preferred by the solar
data and consistent with the oscillation description of the atmospheric
neutrino data, are ruled out by the first results of the KamLAND reactor
experiment, at more than 3_sigma.Comment: 19 pages, LaTeX file using Elsart, 2 tables and 4 figures included.
This version updates the one published in Nucl.Phys.B629:479-490,2002 by
including the new KamLAND dat
Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach
We report about an analytic study involving the {\em intermediate} wave
packet formalism for quantifying the physically relevant information which
appear in the neutrino two-flavor conversion formula and help us to obtain more
precise limits and ranges for neutrino flavor oscillation. By following the
sequence of analytic approximations where we assume a strictly peaked momentum
distribution and consider the second-order corrections in a power series
expansion of the energy, we point out a {\em residual} time-dependent phase
which, coupled with the {\em spreading/slippage} effects, can subtly modify the
neutrino oscillation parameters and limits. Such second-order effects are
usually ignored in the relativistic wave packet treatment, but they present an
evident dependence on the propagation regime so that some small modifications
to the oscillation pattern, even in the ultra-relativistic limit, can be
quantified. These modifications are implemented in the confront with the
neutrino oscillation parameter range (mass-squared difference \Delta m^{\2}
and the mixing-angle ) where we assume the same wave packet parameters
previously noticed in the literature in a kind of {\em toy model} for some
reactor experiments. Generically speaking, our analysis parallels the recent
experimental purposes which concern with higher precision parameter
measurements. To summarize, we show that the effectiveness of a more accurate
determination of \Delta m^{\2} and depends on the wave packet width
and on the averaged propagating energy flux which still
correspond to open variables for some classes of experiments. \Comment: 25 pages, 5 figure
Status of a Supersymmetric Flavour Violating Solution to the Solar Neutrino Puzzle with Three Generations
We present a general study of a three neutrino flavour transition model based
on the supersymmetric interactions which violate R-parity. These interactions
induce flavour violating scattering reactions between solar matter and
neutrinos. The model does not contain any vacuum mass or mixing angle for the
first generation neutrino. Instead, the effective mixing in the first
generation is induced via the new interactions. The model provides a natural
interpretation of the atmospheric neutrino anomaly, and is consistent with
reactor experiments. We determine all R-parity violating couplings which can
contribute to the effective neutrino oscillations, and summarize the present
laboratory bounds. Independent of the specific nature of the (supersymmetric)
flavour violating model, the experimental data on the solar neutrino rates and
the recoil electron energy spectrum are inconsistent with the theoretical
predictions. The confidence level of the -analysis ranges between and . The incompatibility, is due to the new SNO
results, and excludes the present model. We conclude that a non-vanishing
vacuum mixing angle for the first generation neutrino is necessary in our
model. We expect this also to apply to the solutions based on other flavour
violating interactions having constraints of the same order of magnitude.Comment: 17 pages, Latex fil
Light Lambda-Lambda Hypernuclei and the Onset of Stability for Lambda-Xi Hypernuclei
New Faddeev-Yakubovsky calculations for light Lambda-Lambda hypernuclei are
presented in order to assess the self consistency of the Lambda-Lambda
hypernuclear binding-energy world data and the implied strength of the
Lambda-Lambda interaction, in the wake of recent experimental reports on
Lambda-Lambda-4H and Lambda-Lambda-6He. Using Gaussian soft-core simulations of
Nijmegen one-boson-exchange model interactions, the Nijmegen soft-core model
NSC97 simulations are found close to reproducing the recently reported binding
energy of Lambda-Lambda-6He, but not those of other species. For stranger
systems, Faddeev calculations of light Lambda-Xi hypernuclei, using a
simulation of the strongly attractive Lambda-Xi interactions due to the same
model, suggest that Lambda-Xi-6He marks the onset of nuclear stability for Xi
hyperons.Comment: 5 pages, 3 postscript figures; fig.2 replaced, minor changes,
accepted as Rapid Communication in PR
Atmospheric Neutrino Oscillations and New Physics
We study the robustness of the determination of the neutrino masses and
mixing from the analysis of atmospheric and K2K data under the presence of
different forms of phenomenologically allowed new physics in the nu_mu--nu_tau
sector. We focus on vector and tensor-like new physics interactions which allow
us to treat, in a model independent way, effects due to the violation of the
equivalence principle, violations of the Lorentz invariance both CPT conserving
and CPT violating, non-universal couplings to a torsion field and non-standard
neutrino interactions with matter. We perform a global analysis of the full
atmospheric data from SKI together with long baseline K2K data in the presence
of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together
with sub-dominant effects due to these forms of new physics. We show that
within the present degree of experimental precision, the extracted values of
masses and mixing are robust under those effects and we derive the upper bounds
on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include
Current Status of the Resonant Spin-Flavor Precession Solution to the Solar Neutrino Problem
We discuss the current status of the resonant spin-flavor precession (RSFP)
solution to the solar neutrino problem. We perform a fit to all the latest
solar neutrino data for various assumed magnetic field profiles in the sun. We
show that the RSFP can account for all the solar neutrino experiments, giving
as good fit as other alternative solutions such as MSW or Just so, and
therefore can be a viable solution to the solar neutrino problemComment: RevTex file, 9 pages, 12 postscript figures, Some errors are
corrected, some changes in results but no change in conclusions, version to
appear in Astroparticle Physic
Can lepton flavor violating interactions explain the LSND results?
If the atmospheric and the solar neutrino problem are both explained by
neutrino oscillations, and if there are only three light neutrinos, then all
mass-squared differences between the neutrinos are known. In such a case,
existing terrestrial neutrino oscillation experiments cannot be significantly
affected by neutrino oscillations, but, in principle there could be an anomaly
in the neutrino flux due to new neutrino interactions. We discuss how a
non-standard muon decay would modify the
neutrino production processes of these experiments. Since violation
is small for New Physics above the weak scale one can use related
flavor-violating charged lepton processes to constrain these decays in a model
independent way. We show that the upper bounds on ,
muonium-antimuonium conversion and rule out any observable
effect for the present experiments due to
for , respectively. Applying similar arguments to
flavor-changing semi-leptonic reactions we exclude the possibility that the
"oscillation signals" observed at LSND are due to flavor-changing interactions
that conserve total lepton number.Comment: 21 pages, 6 figures, Latex; minor correction
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