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 $\theta_{12} > \pi/4$. For the atmospheric data we perform our analysis of the contained events and the upward-going $\nu$-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 $\theta_{12}$, $\Delta m^2_{21}$ and $\theta_{23}$, $\Delta m^2_{32}$, respectively, as a function of $\theta_{13}$ and determine the constraints from atmospheric and solar data on the mixing angle $\theta_{13}$, 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 ($\phi$) with its duplicate ($\phi^\prime$) and a singly charged scalar ($h^+$), can utilize two global symmetries associated with the conservation of the numbers of $\phi$ and $\phi^\prime$, $N_{\phi,\phi^\prime}$, where $N_\phi+N_{\phi^\prime}$ coincides with the hypercharge while $N_\phi-N_{\phi^\prime}$ ($\equiv X$) is a new conserved charge, which is identical to $L_e-L_\mu-L_\tau$ for the left-handed leptons. Charged leptons turn out to have $e$-$\mu$ and $e$-$\tau$ 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 $s$ with $X$=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 $h^+$ with $X$ = 0; 3) the large solar neutrino mixing is finally induced by a $\nu_\mu$-$\nu_\tau$ mixing arising from the rotation of the radiative mass terms as a result of the diagonalization that converts $e$-$\mu$ and $e$-$\tau$ mixing masses into the electron mass.Comment: RevTex, 10 pages including one figure page, to be published in Int. J. Mod. Phys. A (2002