Neutrino mass spectrum and lepton mixing

The program of reconstruction of the neutrino mass and flavor spectrum is outlined and the present status of research is summarized. We describe the role of future solar and atmospheric neutrino experiments, detection of the Galactic supernovae and double beta decay searches in accomplishing this program. The LSND result and four neutrino mass spectra are considered in connection with recent searches for the sterile components in the solar and atmospheric neutrino fluxes.Comment: 8 pages, latex, 4 figures. Talk given at the XIX International Conference on Neutrino Physics and Astrophysics, Neutrino-2000, Sudbury, Canada, 16 - 21 June 200

Axino-Neutrino Mixing in Gauge-Mediated Supersymmetry Breaking Models

When the strong CP problem is solved by spontaneous breaking of an anomalous global symmetry in theories with gauge-mediated supersymmetry breaking, the pseudo Goldstone fermion (the axino) is a good candidate of a light sterile neutrino. Its mixing with neutrinos relevant for current neutrino experiments can arise in the presence of R-parity violation. The realistic four neutrino mass matrix is obtained when the see-saw mechanism is brought in, and an ansatz for the right-handed neutrino mass is constructed.Comment: Revtex, 7 pp. Version to appear in Phys. Lett.

Non-Oscillation Searches of Neutrino Mass in the Age of Oscillations

We focus on the implications of the oscillations for the shape of nuclear beta-spectrum (=direct search for nu mass). This is of interest because of the existing bound, m_(nu_e)<2.2 eV, that could improve by one order of magnitude with future experiments. We stress important connections with the results of Liquid Scintillator Neutrino Detector, nu_e disappearance experiments, supernova neutrinos and neutrinoless double beta decay.Comment: 3 pages, 1 figure. Matches the version to appear in the Proceedings of NOW 2000 Worksho

Neutrinoless double beta decay, solar neutrinos and mass scales

We obtain bounds for the neutrino masses by combining atmospheric and solar neutrino data with the phenomenology of neutrinoless double beta decay where hypothetical values of || are envisaged from future 0\nu\beta\beta-experiments. Different solutions for the solar neutrino data are considered. For the Large-Mixing-Angle solution, a bound || \leq 0.01 eV would strongly disfavour an inverted hierarchy of the neutrino masses.Comment: 14 pages, including 6 figures; v2: some polishing, additional references, version to appear in Phys. Lett.

Search for τ→μ+γ\tau\to\mu+\gamma decay at Super c−τc -\tau factory

A Monte Carlo study of possible background processes in a search for $\tau \to \mu \gamma$ decay has been performed for conditions of the Super $c-\tau$ factory (CTF) (at a center-of-mass energy 3.686 GeV, 3.77 GeV and 4.17 GeV). The background from $\tau^{+}\tau^{-}$ events has been analysed. Selection criteria for background suppression are suggested and necessary requirements on the detector characteristics have been found. The CTF can successfully compete with the Super B-factory in a search for $\tau \to \mu \gamma$ decay.Comment: 3 pages, 1 figures; contribution to the Proceedings of the PHIPSI11 Workshop (Novosibirsk, Russia, 19-22 September 2011

Unknowns after the SNO Charged-Current Measurement

We perform a model-independent analysis of solar neutrino flux rates including the recent charged-current measurement at the Sudbury Neutrino Observatory (SNO). We derive a universal sum rule involving SNO and SuperKamiokande rates, and show that the SNO neutral-current measurement can not fix the fraction of solar $\nu_e$ oscillating to sterile neutrinos. The large uncertainty in the SSM $^8$B flux impedes a determination of the sterile neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC measuremen

Systematic Approach to Gauge-Invariant Relations between Lepton Flavor Violating Processes

We analyze four-lepton contact interactions that lead to lepton flavor violating processes, with violation of individual family lepton number but total lepton number conserved. In an effective Lagrangian framework, the assumption of gauge invariance leads to relations among branching ratios and cross sections of lepton flavor violating processes. In this paper, we work out how to use these relations systematically. We also study the consequences of loop-induced processes.Comment: 17 pages, 1 figure, 5 table

Anomalous diffusion modifies solar neutrino fluxes

Density and temperature conditions in the solar core suggest that the microscopic diffusion of electrons and ions could be nonstandard: Diffusion and friction coefficients are energy dependent, collisions are not two-body processes and retain memory beyond the single scattering event. A direct consequence of nonstandard diffusion is that the equilibrium energy distribution of particles departs from the Maxwellian one (tails goes to zero more slowly or faster than exponentially) modifying the reaction rates. This effect is qualitatively different from temperature and/or composition modification: Small changes in the number of particles in the distribution tails can strongly modify the rates without affecting bulk properties, such as the sound speed or hydrostatic equilibrium, which depend on the mean values from the distribution. This mechanism can considerably increase the range of predictions for the neutrino fluxes allowed by the current experimental values (cross sections and solar properties) and can be used to reduce the discrepancy between these predictions and the solar neutrino experiments.Comment: 16 pages, ReVTeX, no figures. Text partially revised (24 april 1998

Resolving the Solar Neutrino Problem with KamLAND

We study how well KamLAND, the first terrestrial neutrino experiment capable of addressing the solar neutrino problem, will perform in ascertaining whether or not the large mixing angle MSW solution (with $10^{-5}<\Delta m_{21}^2< 10^{-4} eV^2$ and oscillation amplitude $sin^2 2 \theta_{12}>0.3$) is correct. We find that in a year of operation KamLAND will provide unequivocal evidence for or against this solution. Furthermore, its sensitivity to the three-neutrino oscillation parameters in this region is sufficiently acute as to determine $\Delta m_{21}^2$ to approximately $\pm 10$ % (for $sin^2 2 \theta_{12}>0.7$) and to fix $sin^2 2 \theta_{12}$ to within $\pm 0.1$ (at the $2\sigma$ level) with three years of accumulated data, independent of the value of $\theta_{13}$.Comment: A typographical error is corrected. "3\sigma" is replaced by "2\sigma" everywher

Currents and charges for mixed fields

We present an analysis of currents and charges for a system of two mixed fields, both for spinless bosons and for Dirac fermions. This allows us to obtain in a straightforward way the exact field theoretical oscillation formulas exhibiting corrections with respect to the usual ones derived in quantum mechanics.Comment: 4 pages, RevTe