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[en] We discuss a possibility that the so-called reactor antineutrino anomaly can be, at least in part, explained by applying a quantum field-theoretical approach to neutrino oscillations, which in particular predicts a small deviation from the classical inverse-square law at short but macroscopic distances between the neutrino source and detector. An extensive statistical analysis of the reactor data is performed to examine this speculation.
[en] We formulate direct, neutrino flavor-changing interactions in a framework that fits smoothly with the parametrization of two- and three-state mixing of massive neutrino states. We show that even small direct interaction strengths could have important consequences on the interpretation of currently running and proposed oscillation experiments. The oscillation amplitude and the borders of the allowed regions in two- and three-flavor mixing parameter space can be sensitive to the presence of direct interactions when the transition probability is small. We use extensively the high sensitivity of the NOMAD experiment to illustrate potentially large effects from small, direct flavor violation. In the purely leptonic sector, we find that the clean νμ and νe beams from a μ+-μ- collider could provide the sharpest tests of direct flavor violation. (c) 2000 The American Physical Society
[en] The ν(bar sign)e flux and spectrum have been measured at a distance of about 800 m from the reactors of the Palo Verde Nuclear Generating Station using a segmented Gd-loaded liquid scintillator detector. Correlated positron-neutron events from the reaction ν(bar sign)ep→e+n were recorded for a period of 200 d including 55 d with one of the three reactors off for refueling. Backgrounds were accounted for by making use of the reactor-on and reactor-off cycles, and also with a novel technique based on the difference between signal and background under reversal of the e+ and n portions of the events. A detailed description of the detector calibration, background subtraction, and data analysis is presented here. Results from the experiment show no evidence for neutrino oscillations. ν(bar sign)e→ν(bar sign)x oscillations were excluded at 90% C.L. for Δm2>1.12x10-3 eV2 for full mixing and sin22θ>0.21 for large Δm2. These results support the conclusion that the observed atmospheric neutrino oscillations do not involve νe. (c) 2000 The American Physical Society
[en] Within the framework of three-flavor neutrino oscillations, we consider the physics potential of νe→νμ appearance and νμ→νμ survival measurements at a neutrino factory for a leading oscillation scale δm2∼3.5x10-3 eV2. Event rates are evaluated versus baseline and stored muon energy, and optimal values discussed. Over a sizable region of oscillation parameter space, matter effects would enable the sign of δm2 to be determined from a comparison of νe→νμ with ν(bar sign)e→ν(bar sign)μ event rates and energy distributions. It is important, therefore, that both positive and negative muons can be stored in the ring. Measurements of the νμ→νμ survival spectrum could determine the magnitude of δm2 and the leading oscillation amplitude with a precision of O (1%-2%). (c) 2000 The American Physical Society
[en] We discuss a new method to extract neutrino signals in low-energy experiments. In this scheme the symmetric nature of most backgrounds allows for direct cancellation from data. The application of this technique to the Palo Verde reactor neutrino oscillation experiment allows us to reduce the measurement errors on the antineutrino flux from ∼20% to ∼10%. We expect this method to substantially improve the data quality in future low background experiments such as KamLAND and LENS. (c) 2000 The American Physical Society
[en] An existing neutrino detector (CCFR) and a specially constructed second detector are used to search for a disappearance of flux from the narrow band muon neutrino beam at FNAL. The detectors are located 715 m and 1116 m from the source of 40-230 GeV neutrinos, thus making the experiment sensitive to the oscillation parameters 10 < deltam2 < 1000 eV2 for sin22theta>=0.05. A report on the status of the data analysis is presented
[en] In light of the recent results from the OPERA Collaboration, indicating that neutrinos can travel superluminally, I review a simple extra-dimensional strategy for accommodating such behavior; and I also explain why it is hard in this strategy to avoid violating the null energy condition somewhere in the extra dimensions.
[en] In this talk, we discuss the prospects of determining the neutrino mass hierarchy in future long-baseline oscillation experiments in the light of recently discovered moderately large value of θ13