W. R. Kropp

Limits on neutrino oscillations from the CHOOZ experiment

Abstract We present new results based on the entire CHOOZ (The CHOOZ experiment is named after the new nuclear power station operated by Electricite de France (EdF) near the village of Chooz in the Ardennes region of France) data sample. We find (at 90% confidence level) no evidence for neutrino oscillations in the ν e disappearance mode, for the parameter region given by approximately δm 2 >7·10 −4 eV 2 for maximum mixing, and sin22θ=0.10 for large δm2. 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 ν e flux, the cross section, the number of target protons and the detector efficiencies.

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

Abstract. This final article about the CHOOZ experiment presents a complete description of the

Indications of neutrino oscillation in a 250 km long-baseline experiment.

\bar{\nu}_e

Initial results from the CHOOZ long baseline reactor neutrino oscillation experiment

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.

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

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Limits on the flux of energetic neutrinos from the sun

Abstract Initial results are presented from CHOOZ 1 , a long-baseline reactor-neutrino vacuum-oscillation experiment. The data reported here were taken during the period March to October 1997, when the two reactors ran at combined power levels varying from zero to values approaching their full rated power of 8.5 GW (thermal). Electron antineutrinos from the reactors 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 ν e disappearance mode for the parameter region given approximately by Δm 2 >0.9 10 −3 eV 2 for maximum mixing and sin22θ>0.18 for large Δm2.Initial results are presented from CHOOZ , a long-baseline reactor-neutrino vacuum-oscillation experiment. The data reported here were taken during the period March to October 1997, when the two reactors ran at combined power levels Ž . varying from zero to values approaching their full rated power of 8.5 GW thermal . Electron antineutrinos from the reactors 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 Ž . neutrino event rates, we find at 90% confidence level no evidence for neutrino oscillations in the n disappearance mode e 1 ́ Ž . The CHOOZ experiment is named after the new nuclear power station operated by Electricite de France EdF near the village of Chooz ́ in the Ardennes region of France. 0370-2693r98r

IMB-3: a large water Cherenkov detector for nucleon decay and neutrino interactions

19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII S0370-2693 97 01476-7 ( ) M. Apollonio et al.rPhysics Letters B 42

Near muon range detector for the K2K experiment: Construction and performance

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.

A waveshifter light collector for a water Cherenkov detector

Abstract A number of authors have proposed mechanisms by which the sun could be a strong source of energetic neutrinos. We search for an excess signal of penetrating neutral particles from the direction of the sun. We employ two data samples. One sample studies energies from 400 MeV to 2 GeV. The other studies v μ interactions above 2 GeV where the atmospheric background is lower. Our results are compared with the general background of atmospheric neutrinos from other directions. No significant excess has been found. These results can be used to set limits on possible dark matter candidates.

The IMB photomultiplier test facility

Abstract The IMB experiment, a large water Cherenkov detector which began data collection in September 1982, has undergone several upgrades to improve light collection, on-line processing power, data throughput and buffering, calibration, and operating efficiency. The current device, known as IMB-3, enjoys a factor of four light collection advantage over its precursor. Since May 1986, it has been used to search for such diverse phenomena as nucleon decay, dark matter, neutrino oscillation, and magnetic monopoles, and to study stellar collapse and cosmic rays. Due to its large size and long exposure time IMB presents unique challenges. The design and operation of the IMB-3 detector are described in detail.