Super-Kamiokande atmospheric neutrino data, zenith distributions, and three-flavor oscillations

We present a detailed analysis of the zenith angle distributions of atmospheric neutrino events observed in the Super-Kamiokande (SK) underground experiment, assuming two-flavor and three-flavor oscillations (with one dominant mass scale) among active neutrinos. In particular, we calculate the five angular distributions associated to sub-GeV and multi-GeV \mu-like and e-like events and to upward through-going muons, for a total of 30 accurately computed observables (zenith bins). First we study how such observables vary with the oscillation parameters, and then we perform a fit to the experimental data as measured in SK for an exposure of 33 kTy (535 days). In the two-flavor mixing case, we confirm the results of the SK Collaboration analysis, namely, that \nu_\mu\nu_\tau oscillations are preferred over \nu_\mu\nu_e, and that the no oscillation case is excluded with high confidence. In the three-flavor mixing case, we perform our analysis with and without the additional constraints imposed by the CHOOZ reactor experiment. In both cases, the analysis favors a dominance of the \nu_\mu\nu_\tau channel. Without the CHOOZ constraints, the amplitudes of the subdominant \nu_\munu_e and \nu_e\nu_\tau transitions can also be relatively large, indicating that, at present, current SK data do not exclude sizable \nu_e mixing by themselves. After combining the CHOOZ and SK data, the amplitudes of the subdominant transitions are constrained to be smaller, but they can still play a nonnegligible role both in atmospheric and other neutrino oscillation searches. In particular, we find that the \nu_e appearance probability expected in long baseline experiments can reach the testable level of ~15%.Comment: 35 pages (RevTeX), including 20 ps figures (with epsfig.sty

Global analysis of three-flavor neutrino masses and mixings

We present a comprehensive phenomenological analysis of a vast amount of data from neutrino flavor oscillation and non-oscillation searches, performed within the standard scenario with three massive and mixed neutrinos, and with particular attention to subleading effects. The detailed results discussed in this review represent a state-of-the-art, accurate and up-to-date (as of August 2005) estimate of the three-neutrino mass-mixing parameters.Comment: Final version (including a new Appendix), to be published in "Progress in Particle and Nuclear Physics". Higher-resolution pdf file and eps figures can be download from http://www.ba.infn.it/~now2004/PPNP_review

Three-flavor solar neutrino oscillations with terrestrial neutrino constraints

We present an updated analysis of the current solar neutrino data in terms of three-flavor oscillations, including the additional constraints coming from terrestrial neutrino oscillation searches at the CHOOZ (reactor), Super-Kamiokande (atmospheric), and KEK-to-Kamioka (accelerator) experiments. The best fit is reached for the subcase of two-family mixing, and the additional admixture with the third neutrino is severely limited. We discuss the relevant features of the globally allowed regions in the oscillation parameter space, as well as their impact on the amplitude of possible CP-violation effects at future accelerator experiments and on the reconstruction accuracy of the mass-mixing oscillation parameters at the KamLAND reactor experiment.Comment: 10 pages + 8 figure

Supernova neutrinos: Strong coupling effects of weak interactions

In core-collapse supernovae, neutrinos and antineutrinos are initially subject to significant self-interactions induced by weak neutral currents, which may induce strong-coupling effects on the flavor evolution (collective transitions). The interpretation of the effects is simplified when self-induced collective transitions are decoupled from ordinary matter oscillations, as for the matter density profile that we discuss. In this case, approximate analytical tools can be used (pendulum analogy, swap of energy spectra). For inverted neutrino mass hierarchy, the sequence of effects involves: synchronization, bipolar oscillations, and spectral split. Our simulations shows that the main features of these regimes are not altered when passing from simplified (angle-averaged) treatments to full, multi-angle numerical experiments.Comment: Proceedings of NO-VE 2008, IV International Workshop on "Neutrino Oscillations in Venice" (Venice, Italy, April 15-18, 2008), edited by M. Baldo Ceolin (University of Padova publication, Papergraf Editions, Padova, Italy, 2008), pages 233-24

Addendum to: Model-dependent and -independent implications of the first Sudbury Neutrino Observatory results

In the light of recent experimental and theoretical improvements, we review our previous model-independent comparison [hep-ph/0106247] of the Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) solar neutrino event rates, including updated values for the ``equalized'' SK datum and for the reference Standard Solar Model (SSM) B neutrino flux. We find that the joint SK+SNO evidence for active neutrino flavor transitions is confirmed at the level of 3.3 standard deviations, independently of possible transitions to sterile states. Barring sterile neutrinos, we estimate the 3-sigma range for the $^8$B neutrino flux (normalized to SSM) as f_B=0.96 +0.54-0.55. Accordingly, the 3-sigma range for the energy-averaged nu_e survival probability is found to be = 0.31 +0.55-0.16, independently of the functional form of P_ee. An increase of the reference nu_e + d --> p + p + e cross section by ~3%, as suggested by recent theoretical calculations, would slightly shift the central values of f_B and of to ~1.00 and ~0.29, respectively, and would strengthen the model-independent evidence for nu_e transitions into active states at the level of ~3.6 sigma.Comment: 6 pages + 2 figures. Addendum to hep-ph/010624

Mantle geoneutrinos in KamLAND and Borexino

The KamLAND and Borexino experiments have observed, each at ~4 sigma level, signals of electron antineutrinos produced in the decay chains of thorium and uranium in the Earth's crust and mantle (Th and U geoneutrinos). Various pieces of geochemical and geophysical information allow an estimation of the crustal geoneutrino flux components with relatively small uncertainties. The mantle component may then be inferred by subtracting the estimated crustal flux from the measured total flux. To this purpose, we analyze in detail the experimental Th and U geoneutrino event rates in KamLAND and Borexino, including neutrino oscillation effects. We estimate the crustal flux at the two detector sites, using state-of-the-art information about the Th and U distribution on global and local scales. We find that crust-subtracted signals show hints of a residual mantle component, emerging at ~2.4 sigma level by combining the KamLAND and Borexino data. The inferred mantle flux slightly favors scenarios with relatively high Th and U abundances, within +-1 sigma uncertainties comparable to the spread of predictions from recent mantle models.Comment: Slight changes and improvements in the text & figures. Results unchanged. To appear in Phys. Rev.

The Higgs Boson Mass from Precision Electroweak Data

We present a new global fit to precision electroweak data, including new low- and high-energy data and analyzing the radiative corrections arising from the minimal symmetry breaking sectors of the Standard Model (SM) and its supersymmetric extension (MSSM). It is shown that present data favor a Higgs mass of O(M_Z): M_H = 76+152-50 GeV. We confront our analysis with (meta)stability and perturbative bounds on the SM Higgs mass, and the theoretical upper bound on the MSSM Higgs mass. Present data do not discriminate significantly between the SM and MSSM Higgs mass ranges. We comment in passing on the sensitivity of the Higgs mass determination to the values of alpha(M_Z) and alpha_s(M_Z).Comment: 10 pages, latex, 8 figures as uu-encoded postscript fil

Four-neutrino oscillation solutions of the atmospheric neutrino anomaly

In the context of neutrino scenarios characterized by four (three active plus one sterile) neutrino species and by mass spectra with two separated doublets, we analyze solutions to the atmospheric neutrino anomaly which smoothly interpolate between \nu_\mu-->\nu_\tau and \nu_\mu-->\nu_s oscillations. We show that, although the Super-Kamiokande data disfavor the pure \nu_\mu-->\nu_s channel, they do not exclude its occurrence, with sizable amplitude, in addition to the \nu_\mu-->\nu_\tau channel. High energy muon data appear to be crucial in assessing the relative amplitude of active and sterile neutrino oscillations. It is also qualitatively shown that such atmospheric \nu solutions are compatible with analogous solutions to the solar neutrino problem, which involve oscillations of \nu_e in both sterile and active states.Comment: Added references. Accepted for publication in Phys. Rev.