L. R. Price

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

Initial results from the CHOOZ long baseline reactor neutrino oscillation experiment

\bar{\nu}_e

Neutrino measurements with the IMB director

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

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

Neutrino-induced deuteron disintegration experiment

The measure fraction of muon-like, single-track, atmospheric neutrino events over a 7.7 kton-yr exposure of IMB is 0.36±0.02(stat)±0.02(syst) as compared to an expectation of 0.51±0.01(stat)±0.05(syst). No significant dependence of this fraction on zenith angle or momentum is seen. In addition, upward-going muons from higher energy atmospheric neutrino interactions are used to search for vμ oscillations into vτ by comparing the measured rate with the expected rate from a conservative flux calculation. The ratio of upward-going muons which stop in the detector to those which exit is also used to search for deviations from the expected energy spectrum. No evidence for oscillations is found in either analysis. Finally, a search is made for an astrophysical component to the detected neutrino flux from both energetic point sources and gamma-ray bursts and also for a possible seasonal variation of the high energy neutrino flux due to atmospheric density changes. No evidence for any of these effects if found.

Four-pion final state in pp annihilations at 0.7 to 1.1 GeV/c☆

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.

Calibration of the IMB detector

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.

A low-background detector for observing the disintegration of the deuteron by reactor antineutrinos

Cross sections for the disintegration of the deuteron via neutral-current (NCD) and charged-current (CCD) interactions with reactor antineutrinos ({bar {nu}}{sub e}d{r_arrow}{bar {nu}}{sub e}pn and {bar {nu}}{sub e}d{r_arrow}e{sup +}nn) are measured to be 6.08{plus_minus}0.77{times}10{sup {minus}45} cm{sup 2} and 9.83{plus_minus}2.04{times}10{sup {minus}45} cm{sup 2} per neutrino, respectively, in excellent agreement with current calculations. Since the experimental NCD value depends upon the CCD value, if we use the theoretical value for the CCD reaction, we obtain the improved value of 5.98{plus_minus}0.54{times}10{sup {minus}45} for the NCD cross section. The neutral-current reaction allows a unique measurement of the isovector{endash}axial vector coupling constant in the hadronic weak interaction, {beta}. In the standard model, this constant is predicted to be exactly 1, independent of the Weinberg angle. We measure a value of {beta}{sup 2}=1.01{plus_minus}0.16. Using the above improved value for the NCD cross section, {beta}{sup 2} becomes 0.99{plus_minus}0.10. {copyright} {ital 1999} {ital The American Physical Society}