Randolph Reeder

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

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

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.

Noncompact simulations of SU(2)3

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

Comparison of the simplicial method with Wilson's lattice gauge theory for U(1)3

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

Testing two versions of lattice gauge theory: Creutz ratios inU(1)3

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.

Simplicial interpolations for path integrals

Abstract The action density and Wilson loops for SU(2) in three dimensions have been measured using both a noncompact version of lattice gauge theory and Wilsons version. As a standard of comparison, the Creutz ratio χ of a quartet of Wilson loops has been calculated in the exact theory to order 1/β 2 . The noncompact method gave χs that are between 2 and 23% below the one-loop calculation for the smaller loops at β = 30 and 60 on a 24 3 lattice. Wilsons method gave χs that are above the one-loop calculation by comparable amounts. For β ⩽10, the noncompact χs are closer than the Wilson χs to the one-loop calculation. Also some noncompact simulations were done in the temporal gauge; the results agree subtantially with those done without gauge fixing, providing evidence for the gauge independence of the noncompact method. By comparing the χs of the 12 3 lattice at β = 30 with those of the 24 3 lattice at β = 30 and 60, evidence was found that the accuracy of the noncompact method improves both as the volume of the lattice grows and as the lattice spacing shrinks.

Path integrals without lattices

Abstract In the simplicial version of lattice gauge theory, euclidean path integrals are approximated by tiling spacetime with simplexes and by linearly interpolating the fields throughout each simplex from their values at the vertices. This method is compared with Wilsons lattice gauge theory for U(1) in three dimensions. As a standard of comparison, the exact values of Creutz ratios of Wilson loops in the continuum theory are computed. Monte Carlo computations using the simplicial method give Creutz ratios within a few percent of the exact values for reasonably sized loops at β = 1,2,and10. Similar computations using Wilsons method give ratios that typically differ from the exact values by factors of two or more for 1 ⩽ β ⩽ 3.5 and that have the wrong β dependence. The better accuracy of the simplicial method is due to its use of the action and domain of integration of the exact theory, unaltered apart from the granularity of the simplicial lattice. Data on the action density and the mass gap are also presented.

Path integrals without lattices for QED2

In our simplicial version of lattice gauge theory, we approximate Euclidean path integrals by tiling space-time with simplexes and by linearly interpolating the fields throughout each simplex from their values at the vertices. We compare this method with Wilsons lattice gauge theory forU(1) in three dimensions. As a standard of comparison, we compute the exact values of Creutz ratios of Wilson loops in the continuum theory. Monte Carlo computations using the simplicial method give Creutz ratios within a few percent of the exact values for reasonably sized loop atβ=1, 2, and 10. Similar computations using Wilsons method give ratios that typically differ from the exact values by factors of 2 or more for 1⩽β⩽3.5 and that have the wrongβ dependence. The better accuracy of the simplicial method is due to its use of the action and domain of integration of the exact theory, unaltered apart from the granularity of the simplicial lattice. We also present data on the action density and the mass gap.