141 research outputs found
Global three-neutrino oscillation analysis of neutrino data
A global analysis of the solar, atmospheric and reactor neutrino data is
presented in terms of three-neutrino oscillations. We include the most recent
solar neutrino rates of Homestake, SAGE, GALLEX and GNO, as well as the recent
1117 day Super-Kamiokande data sample, including the recoil electron energy
spectrum both for day and night periods and we treat in a unified way the full
parameter space for oscillations, correctly accounting for the transition from
the matter enhanced (MSW) to the vacuum oscillations regime. Likewise, we
include in our description conversions with . For the
atmospheric data we perform our analysis of the contained events and the
upward-going -induced muon fluxes, including the previous data samples of
Frejus, IMB, Nusex, and Kamioka experiments as well as the full 71 kton-yr
(1144 days) Super-Kamiokande data set, the recent 5.1 kton-yr contained events
of Soudan2 and the results on upgoing muons from the MACRO detector. We first
present the allowed regions of solar and atmospheric oscillation parameters
, and , ,
respectively, as a function of and determine the constraints from
atmospheric and solar data on the mixing angle , common to solar
and atmospheric analyses. We also obtain the allowed ranges of parameters from
the full five-dimensional combined analysis of the solar, atmospheric and
reactor data.Comment: 56 pages, 21 postscript figures. Some misprints corrected and new
references added. Chooz limit included in Fig.21. Final version to appear in
Phys. Rev.
Seasonal Dependence in the Solar Neutrino Flux
MSW solutions of the solar neutrino problem predict a seasonal dependence of
the zenith angle distribution of the event rates, due to the non-zero latitude
at the Super-Kamiokande site. We calculate this seasonal dependence and compare
it with the expectations in the no-oscillation case as well as just-so
scenario, in the light of the latest Super-Kamiokande 708-day data. The
seasonal dependence can be sizeable in the large mixing angle MSW solution and
would be correlated with the day-night effect. This may be used to discriminate
between MSW and just-so scenarios and should be taken into account in refined
fits of the data.Comment: 4 pages, latex, RevTeX, two postscript figure
Four-neutrino oscillations and the solar neutrino problem
We perform a fit of solar neutrino data in the framework of the two four-neutrino schemes that are compatible with the results of all neutrino oscillation experiments. These schemes allow simultaneous transitions of solar nu_e's into active nu_mu's, nu_tau's and sterile nu_s. The data imply that the SMA solution is valid for any combination of nu_e->active and nu_e->sterile transitions, whereas the LMA, LOW and VO solutions disappear when nu_e->nu_s transitions are dominant
Before and After: How has the SNO NC measurement changed things?
We present "Before and After" global oscillation solutions, as well as
predicted "Before and After" values and ranges for ten future solar neutrino
observables (for BOREXINO, KamLAND, SNO, and a generic p-p neutrino detector).
We have performed global analyses using the full SNO day-night energy spectrum
and, alternatively, just the SNO CC and NC rates and the day-night
asymmetry.The ``Before'' case includes all solar neutrino data (and some
theoretical improvements) available prior to April 20, 2002 and the ``After''
case includes, in addition, the new SNO data on the CC, NC, and day-night
asymmetry. The LMA solution is the only currently allowed MSW oscillation
solution at ~99% CL. The LOW solution is allowed only at more than 2.5 sigma,
SMA at 3.7 sigma or 4.7 sigma (depending upon analysis strategy), and pure
sterile oscillations at 4.7sigma. Small mixing angles are ``out''(pure sterile
is ``way out''); MSW with large mixing angles is definitely ``in''. Vacuum
oscillations are allowed at 3 sigma, but not a 2 sigma. Precise maximal mixing
is excluded at 3.2 sigma for MSW solutions and at 2.8 sigma for vacuum
solutions. Most of the predicted values for future observables for the
BOREXINO, KamLAND, and future SNO measurements are changed only by minor
amounts by the inclusion of the recent SNO data. In order to test the
robustness of the allowed neutrino oscillation regions and the predictions for
future observables, we have carried out calculations using a variety of
strategies to analyze the SNO and other solar neutrino data.Comment: Added global analysis with full SNO day-night energy spectrum.
Results essentially unchange
Large Solar Neutrino Mixing in an Extended Zee Model
The Zee model, which employs the standard Higgs scalar () with its
duplicate () and a singly charged scalar (), can utilize two
global symmetries associated with the conservation of the numbers of and
, , where coincides
with the hypercharge while () is a new
conserved charge, which is identical to for the left-handed
leptons. Charged leptons turn out to have - and - mixing
masses, which are found to be crucial for the large solar neutrino mixing. In
an extended version of the Zee model with an extra triplet Higgs scalar (s),
neutrino oscillations are described by three steps: 1) the maximal atmospheric
mixing is induced by democratic mass terms supplied by with =2 that can
initiate the type II seesaw mechanism for the smallness of these masses; 2) the
maximal solar neutrino mixing is triggered by the creation of radiative masses
by with = 0; 3) the large solar neutrino mixing is finally induced by
a - mixing arising from the rotation of the radiative mass
terms as a result of the diagonalization that converts - and -
mixing masses into the electron mass.Comment: RevTex, 10 pages including one figure page, to be published in Int.
J. Mod. Phys. A (2002
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