18 research outputs found
Three-Neutrino Mixing and Combined Vacuum Oscillations and MSW Transitions of Solar Neutrinos
Assuming three flavour neutrino mixing takes place in vacuum, we investigate
the possibility that the solar nu_e take part in MSW transitions in the Sun due
to Delta m^2_{31} from 10^{-7} eV^2 to 10^{-4} eV^2, followed by long wave
length vacuum oscillations on the way to the Earth, triggered by Delta m^2_{21}
(or Delta m^2_{32}) from 10^{-12} eV^2 to 10^{-10} eV^2, Delta m^2_{31} and
Delta m^2_{21} (Delta m^2_{32}) being the corresponding neutrino mass squared
differences. The solar nu_e survival probability is shown to be described in
this case by a simple analytic expression. Depending on whether the vacuum
oscillations are due to Delta m^2_{21} or Delta m^2_{32} there are two very
different types of interplay between the MSW transitions and the vacuum
oscillations of the solar nu_e. Performing an analysis of the most recently
published solar neutrino data we have found several qualitatively new solutions
of the solar neutrino problem of the hybrid MSW transitions + vacuum
oscillations type. The solutions differ in the way the pp, 7Be and 8B neutrino
fluxes are affected by the transitions in the Sun and the oscillations in
vacuum. The specific features of the new solutions are discussed.Comment: 37 pages Latex, 16 Postscript Figure
Agro-materials : a bibliographic review
Facing the problems of plastic recycling and fossil resources exhaustion, the use of biomass to conceive new materials appears like a reasonable solution. Two axes of research are nowadays developed : on the one hand the synthesis of biodegradable plastics, whichever the methods may be, on the other hand the utilization of raw biopolymers, which is the object of this paper. From this perspective, the “plastic” properties of natural polymers, the caracteristics of the different classes of polymers, the use of charge in vegetable matrix and the possible means of improving the durability of these agro-materials are reviewed
Neutrino oscillation constraints on neutrinoless double beta decay
We have studied the constraints imposed by the results of neutrino
oscillation experiments on the effective Majorana mass || that characterizes
the contribution of Majorana neutrino masses to the matrix element of
neutrinoless double-beta decay. We have shown that in a general scheme with
three Majorana neutrinos and a hierarchy of neutrino masses (which can be
explained by the see-saw mechanism), the results of neutrino oscillation
experiments imply rather strong constraints on the parameter ||. From the
results of the first reactor long-baseline experiment CHOOZ and the Bugey
experiment it follows that || < 3x10^{-2} eV if the largest mass-squared
difference is smaller than 2 eV^2. Hence, we conclude that the observation of
neutrinoless double-beta decay with a probability that corresponds to || >
10^{-1} eV would be a signal for a non-hierarchical neutrino mass spectrum
and/or non-standard mechanisms of lepton number violation.Comment: 20 pages, including 4 figure
Neutrinoless double-beta decay with three or four neutrino mixing
Considering the scheme with mixing of three neutrinos and a mass hierarchy
that can accommodate the results of solar and atmospheric neutrino experiments,
it is shown that the results of solar neutrino experiments imply a lower bound
for the effective Majorana mass in neutrinoless double-beta decay, under the
natural assumptions that massive neutrinos are Majorana particles and there are
no unlikely fine-tuned cancellations among the contributions of the different
neutrino masses. Considering the four-neutrino schemes that can accommodate
also the results of the LSND experiment, it is shown that only one of them is
compatible with the results of neutrinoless double-beta decay experiments and
with the measurement of the abundances of primordial elements produced in
Big-Bang Nucleosynthesis. It is shown that in this scheme, under the
assumptions that massive neutrinos are Majorana particles and there are no
cancellations among the contributions of the different neutrino masses, the
results of the LSND experiment imply a lower bound for the effective Majorana
mass in neutrinoless double-beta decay.Comment: 18 pages including 2 figures, RevTe