25 research outputs found
Solar neutrino event spectra: Tuning SNO to equalize Super-Kamiokande
The Super-Kamiokande (SK) and the Sudbury Neutrino Observatory (SNO)
experiments are monitoring the flux of B solar neutrinos through the electron
energy spectrum from the reactions nu_{e,mu,tau} + e --> nu_{e,mu,tau} + e and
nu_e + d --> p + p + e, respectively. We show that the SK detector response to
B neutrinos in each bin of the electron energy spectrum (above 8 MeV) can be
approximated, with good accuracy, by the SNO detector response in an
appropriate electron energy range (above 5.1 MeV). For instance, the SK
response in the bin [10,10.5] MeV is reproduced (``equalized'') within 2
percent by the SNO response in the range [7.1,11.75] MeV. As a consequence, in
the presence of active neutrino oscillations, the SK and SNO event rates in the
corresponding energy ranges turn out to be linearly related, for any functional
form of the oscillation probability. Such equalization is not spoiled by the
possible contribution of hep neutrinos (within current phenomenological
limits). In perspective, when the SK and the SNO spectra will both be measured
with high accuracy, the SK-SNO equalization can be used to determine the
absolute B neutrino flux, and to cross-check the (non)observation of spectral
deviations in SK and SNO. At present, as an exercise, we use the equalization
to ``predict'' the SNO energy spectrum, on the basis of the current SK data.
Finally, we briefly discuss some modifications or limitations of our results in
the case of sterile neutrino oscillations and of relatively large Earth matter
effects.Comment: 18 pages + 6 figure
Three-flavor MSW solutions of the solar neutrino problem
We perform an updated phenomenological analysis of the
Mikheyev-Smirnov-Wolfenstein (MSW) solutions of the solar neutrino problem,
assuming oscillations between two and three neutrino families. The analysis
includes the total rates of the Homestake, SAGE, GALLEX, Kamiokande and
Super-Kamiokande experiments, as well as the day-night asymmetry and the 18-bin
energy spectrum of Super-Kamiokande. Solutions are found at several values of
the theta_{13} mixing angle. Among the most interesting features, we find that
solar neutrino data alone put the constraint theta_{13} < 55--59 deg at 95%
C.L., and that a fraction of the MSW solutions extends at and beyond maximal
(nu_1,nu_2) mixing (theta_{12} > pi/4), especially if the neutrino square mass
splitting is in its lower range (m^2_2-m^2_1 ~ 10^{-7} eV^2) and if theta_{13}
is nonzero. In particular, bimaximal (or nearly bimaximal) mixing is possible
for atmospheric and MSW solar neutrino oscillations within the stringent
reactor bounds on theta_{13}.Comment: 19 pages (RevTeX) + 14 figures (PostScript
Neutrino Masses and Mixing: Evidence and Implications
Measurements of various features of the fluxes of atmospheric and solar
neutrinos have provided evidence for neutrino oscillations and therefore for
neutrino masses and mixing. We review the phenomenology of neutrino
oscillations in vacuum and in matter. We present the existing evidence from
solar and atmospheric neutrinos as well as the results from laboratory
searches, including the final status of the LSND experiment. We describe the
theoretical inputs that are used to interpret the experimental results in terms
of neutrino oscillations. We derive the allowed ranges for the mass and mixing
parameters in three frameworks: First, each set of observations is analyzed
separately in a two-neutrino framework; Second, the data from solar and
atmospheric neutrinos are analyzed in a three active neutrino framework; Third,
the LSND results are added, and the status of accommodating all three signals
in the framework of three active and one sterile light neutrinos is presented.
We review the theoretical implications of these results: the existence of new
physics, the estimate of the scale of this new physics and the lessons for
grand unified theories, for supersymmetric models with R-parity violation, for
models of extra dimensions and singlet fermions in the bulk, and for flavor
models.Comment: Added note on the effects of KamLAND results. Two new figure