Initial Results from the CHOOZ Long Baseline Reactor Neutrino Oscillation Experiment

Initial results are presented from CHOOZ, a long-baseline reactor-neutrino vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid scintillation calorimeter located at a distance of about 1 km. The detector was constructed in a tunnel protected from cosmic rays by a 300 MWE rock overburden. This massive shielding strongly reduced potentially troublesome backgrounds due to cosmic-ray muons, leading to a background rate of about one event per day, more than an order of magnitude smaller than the observed neutrino signal. From the statistical agreement between detected and expected neutrino event rates, we find (at 90% confidence level) no evidence for neutrino oscillations in the electron antineutrino disappearance mode for the parameter region given approximately by deltam**2 > 0.9 10**(-3) eV**2 for maximum mixing and (sin(2 theta)**2) > 0.18 for large deltam**2.Comment: 13 pages, Latex, submitted to Physics Letters

Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station

This final article about the CHOOZ experiment presents a complete description of the electron antineutrino source and detector, the calibration methods and stability checks, the event reconstruction procedures and the Monte Carlo simulation. The data analysis, systematic effects and the methods used to reach our conclusions are fully discussed. Some new remarks are presented on the deduction of the confidence limits and on the correct treatment of systematic errors.Comment: 41 pages, 59 figures, Latex file, accepted for publication by Eur.Phys.J.

Limits on Neutrino Oscillations from the CHOOZ Experiment

We present new results based on the entire CHOOZ data sample. We find (at 90% confidence level) no evidence for neutrino oscillations in the anti_nue disappearance mode, for the parameter region given by approximately Delta m**2 > 7 x 10**-4 eV^2 for maximum mixing, and sin**2(2 theta) = 0.10 for large Delta m**2. Lower sensitivity results, based only on the comparison of the positron spectra from the two different-distance nuclear reactors, are also presented; these are independent of the absolute normalization of the anti_nue flux, the cross section, the number of target protons and the detector efficiencies.Comment: 19 pages, 11 figures, Latex fil

Determination of neutrino incoming direction in the CHOOZ experiment and Supernova explosion location by scintillator detectors

The CHOOZ experiment measured the antineutrino flux at a distance of about 1 Km from two nuclear reactors in order to detect possible neutrino oscillations with squared mass differences as low as 10**-3 eV**2 for full mixing. We show that the data analysis of the electron antineutrino events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture of about 18 degrees at the 68% C.L.. We discuss the implications of this experimental result for tracking down a supernova explosion.Comment: Submitted to Physical Review

Determination of neutrino incoming direction in the CHOOZ experiment and its application to supernova explosion location by scintillator detectors

The CHOOZ experiment has measured the antineutrino flux at about 1 km from two nuclear reactors to search for possible (e)-->(x) oscillations with mass-squared differences as low as 10(-3) eV(2) for full mixing. We show that the analysis of the similar to 2700 (e) events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture approximate to 18 degrees at the 68% C.L. We discuss the implications of this result for locating a supernova explosion

Determination of neutrino incoming direction in the CHOOZ experiment and its application to Supernova explosion location by scintillator detectors

The CHOOZ experiment 1 has measured the antineutrino flux at about 1 Km from two nuclear reactors to search for possible e ! x oscillations with mass-squared differences as low as 10 \Gamma3 eV 2 for full mixing. We show that the analysis of the ¸ 2700 e --events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture ß 18 ffi at the 68% C:L: . We discuss the implications of this result for locating a supernova explosion. 1 Introduction Locating a --source in the sky is of primary importance in the case of galactic supernova (SN) explosions; particularly if the SN is not optically visible, either because it is hidden behind the dust of the galactic disk, or because the light emission follows the neutrino burst by hours or days. In this latter case, an early SN detection and location by neutrinos could allow observation of the evolution of the first optical stages. Several pointing methods have been extensively discusse..