3 research outputs found
Atmospheric neutrino oscillations with three neutrinos and a mass hierarchy
A comprehensive formalism for the description of neutrino oscillations in the
Earth in a general scheme with three massive neutrinos and the mass hierarchy
m_1<<m_2<<m_3 is presented. Using this formalism, which is valid both in vacuum
and in a medium, the matter effect on the oscillations of low-energy neutrinos
is discussed, pointing out the existence of very long oscillations which are
independent of the neutrino masses and the neutrino energy, and are very
sensitive to the matter density along the neutrino trajectory. As an example of
application of the formulation, a fit of the Kamiokande atmospheric neutrino
data with the matter effect taken into account for neutrinos propagating in the
Earth is presented. The results of the fit indicate that 4*10^{-3} eV^2 < m_3^2
nu_e,
nu_munu_tau, nu_enu_tau) could be large. Hence, long-baseline experiments
with reactor (CHOOZ and Palo Verde) and accelerator (K2K, MINOS and ICARUS)
neutrinos could observe neutrino oscillations in all channels with a relatively
large statistics.Comment: 42 pages, including 7 figure
ARE THERE STERILE NEUTRINOS IN THE FLUX OF SOLAR NEUTRINOS ON THE EARTH?
It is shown that the future SNO and Super-Kamiokande experiments, in which
high energy neutrinos will be detected through the observation
of CC, NC and -- elastic scattering processes, could allow to reveal in
a model independent way the presence of sterile neutrinos in the flux of solar
neutrinos on the earth. Lower bounds for different averaged values of the
probability of transition of solar 's into sterile states and for the
total flux of neutrinos are derived in terms of measurable
quantities. The possibilities to reveal the presence of and/or
in the solar neutrino flux on the earth are also considered and the
case of transitions of solar 's only into sterile states is discussed.
Some numerical results for a simple model with -- mixing are
given.Comment: Revised reference list. Revtex file, 15 pages + 4 figures (included).
The postscript file of text and figures is available at
ftp://toxd01.to.infn.it/pub/giunti/1995/dftt-12-95/dftt-12-95.ps.
Neutrino mass spectrum from the results of neutrino oscillation experiments
All the possible schemes of neutrino mixing with four massive neutrinos
inspired by the existing experimental indications in favor of neutrino mixing
are considered in a model independent way. Assuming that in short-baseline
experiments only one mass-squared difference is relevant, it is shown that the
scheme with a neutrino mass hierarchy is not compatible with the experimental
results. Only two schemes with two pairs of neutrinos with close masses
separated by a mass difference of the order of 1 eV are in agreement with the
results of all experiments. One of these schemes leads to possibly observable
effects in Tritium and neutrinoless double-beta decay experiments.Comment: Latex2e file, 13 pages including 2 figures. Postscript also available
at http://www.to.infn.it/teorici/giunti/papers.htm