Neutrino Oscillation and CP Violation

We reconsider the meaning of observing CP violation in neutrino oscillation.Comment: Talk given at the NUFACT'00: International Workshop on Muon Storage Ring for a Neutrino Factory, Monterey, California, 22-26 May 2000. Several typographical errors are correcte

Recent Results from the K2K (KEK-to-Kamioka) Neutrino Oscillation Experiment

The latest results of the K2K experiment are reported. The results are based on data taken from June, 1999, to June, 2000, corresponding to a total $2.6 \cdot 10^{19}$ protons on target. Twenty seven fully-contained events in the 22.5 kton fiducial volume of Super-Kamiokande (SK) are observed. The expected number of events is estimated to be 40.3^{+4.7}_{-4.6} assuming the null oscillations hypothesis.Comment: 7 pages, 7 figures. Talk given at the Sixth International Workshop on Tau Lepton Physics, Victoria, BC, Canada, September 19, 200

Implications of a Minimal SO(10) Higgs Structure

A minimal SO(10) Higgs structure involving a single adjoint field along with spinors, vectors and singlets has been shown to break the SO(10) gauge symmetry to the standard model while stabilizing the F-flat directions and solving the doublet-triplet splitting problem naturally. With this minimal set of Higgs fields, we show how to construct quark and lepton mass matrices which explain well the many features of the observed spectrum, including the Georgi-Jarlskog mass relations. A large mixing of the muon- and tau-neutrinos results naturally as observed in the atmospheric neutrino data. A particular model relying on a family symmetry has been constructed which realizes the desired mass matrices.Comment: 10 pages, REVTEX, contribution submitted to NEUTRINO 98 Conferenc

Aquatic insects as an energetic subsidy to riparian consumers in the Olman River Basin, Alberta

xii, 126 leaves m ; 29 cmFreshwater and terrestrial ecosystems are connected through biomass exchanges such as the flow of predators, prey, nutrients and detritus between them. Emerging aquatic insects provide an alternate food source to riparian consumers often termed an allochthonous subsidy. Stable isotope analyses of naturally occurring carbon and nitrogen is effective for tracing energetic food sources to consumers. This thesis evaluated whether stable isotope analysis would be effective in the Oldman River Basin, Alberta. Aquatic and riparian primary consumers are distinct in their isotopic signatures and valid for to use in stable isotope analysis. Stable isotope modelling was then used to evaluate the proportional contribution of aquatic insects to riparian spider and beetle diets. Carbon analysis showed an overall aquatic insect contribution of 25 % and 18 % for spiders and beetles, respectively; while nitrogen analysis showed an overall contribution of 36 % and 20 %, respectively. The spatial extent of the aquatic insect contribution upland from the river was shown to decrease from 50 - 55 % at 1 m to 0 % at 30 m for both consumers using carbon, and from 35 - 40 % at 1 m to 0 % at 40 m using nitrogen. Finally, regression modelling of the size of a river and the spatial scale of an aquatic insect dietary contribution showed a significant relationship, indicating larger water bodies support higher production of aquatic insects. A meta-analysis of published literature applied to this model also indicated a significant relationship between the size of the river and the extent of an aquatic insect contribution

Standard and exotic interpretations of the atmospheric neutrino data

The present status of some theoretical interpretations of the atmospheric neutrino deficit is briefly discussed. Specifically, we show the results for the FC mechanism and for the standard oscillation hypothesis, both in the active and in the sterile channels. All these mechanisms are able to fit the present data to a good statistical level. Among them, the nu_mu --> nu_tau oscillation is certainly the best explanation to the atmospheric neutrino deficit, providing a remarkably good agreement with the data.Comment: 3 pages, 2 figures, talk delivered at the 6th International Workshop on Topics in Astroparticle and Underground Physics (TAUP 99), September 1999, Paris, (to appear in the Conference Proceedings, Nucl. Phys. B (Proc. Suppl.), eds. M. Froissart, J. Dumarchez and D. Vignaud

Constraints on long-baseline neutrino oscillations from the results of neutrino oscillation experiments

It is shown that in the two schemes with four massive neutrinos which are compatible with the results of all neutrino oscillation experiments, the probabilities of nu_e disappearance and nu_mu->nu_e appearance in long-baseline experiments are severely constrained.Comment: 7 pages, including 2 figures. Talk presented by C. Giunti at TAUP97, September 7-11, 1997, Laboratori Nazionali del Gran Sasso, Ital

The Standard Model of Particle Physics. Neutrino Oscillations

The Standard Model (SM) of Particle Physics was tested to great precision by experiments at the highest energy colliders (LEP, Hera, Tevatron, SLAC). The only missing particle is the Higgs boson, which will be the first particle to be searched for at the new Large Hadron Collider (LHC) at CERN. The SM anticipated that there are 3 types of left handed neutrinos. Experiments on atmospheric and solar neutrinos (made in Japan, Italy, Canada, Russia and the US) have shown the existence of neutrino oscillations, which imply that neutrinos have very small mass differences and violate the conservation of individual leptonic numbers. Neutrino oscillations were verified in long baseline neutrino experiments (in Japan and in the USA); and cosmology has given reasonably precise indications on the sum of the neutrino masses. In this general lecture will be summarized some of the main properties of the SM and some of the main results obtained in the field and the experiments in preparation. Some of the main open questions will be briefly discussed.Comment: 6 pages, 13 EPS figures. Special lecture given at the 24th ICNTS Conference, 1-5 September 2008, Bologna, Italy. Changed reference

Atmospheric neutrino results from Super-Kamiokande and Kamiokande - Evidence for nu_mu oscillations -

New atmospheric neutrino results from Super-Kamiokande are presented. Results from Kamiokande on upward going muons are also presented. All these data, together with the Kamiokande atmospheric neutrino data give evidence for neutrino oscillations. Two flavor nu_mu nu_tau oscillations, with large sin^2(2theta) and Delta-m^2 in the region of 10^-3 to 10^-2, explain all these data.Comment: 10 pages, 6 figures, to appear in the proceedings of XVIII International Conference on Neutrino Physics and Astrophysics (Neutrino'98), Takayama, Japan, June 199

A 3-Dimensional Calculation of Atmospheric Neutrino Flux

An extensive 3-dimensional Monte Carlo calculation of the atmospheric neutrino flux is in progress with the FLUKA Monte Carlo code. The results are compared to those obtained under the 1-dimensional approximation, where secondary particles and decay products are assumed to be collinear to the primary cosmic ray, as usually done in most of the already existing flux calculations. It is shown that the collinear approximation gives rise to a wrong angular distribution of neutrinos, essentially in the Sub-GeV region. However, the angular smearing introduced by the experimental inability of detecting recoils in neutrino interactions with nuclei is large enough to wash out, in practice, most of the differences between 3-dimensional and 1-dimensional flux calculations. Therefore, the use of the collinear approximation should have not introduced a significant bias in the determination of the flavor oscillation parameters in current experiments.Comment: 27 pages, 14 figures. To be submitted to Astroparticle Physics. To be submitted to Astroparticle Physic

Detection of Accelerator-Produced Neutrinos at a Distance of 250 km

The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time of the beam in the 22.5 kt fiducial volume of Super--Kamiokande, the far detector at 250 km distance. The expectation is 37.8+3.5-3.8, derived using measurements of neutrino interactions in a near detector and extrapolation using a beam simulation validated by a measurement of pion kinematics after production and focusing. The background is of order 10^-3 events.Comment: 6 pages, 3 embedded figures, LaTeX with RevTeX style, submitted to PRL. This version is As Submitte