L. Behr

Study of atmospheric neutrino interactions with the Fréjus detector

Abstract We present an analysis of the neutrino event sample recorded in the Frejus experiment. This sample which corresponds to the 1.56 kt yr final sensitivity of the experiment is compared to the predictions of a Monte Carlo neutrino simulation program. It is based on a recent calculation of the atmospheric neutrino flux at the Frejus latitude which takes into account muon polarization effects. The comparison is performed on the distributions of the visible energy, the zenith angle and the neutrino flavor. Good agreement is obtained between the data and the simulation within statistics.

A study of atmospheric neutrino oscillations in the Fréjus experiment

Abstract Atmospheric neutrino interactions have been studied with the Frejus proton decay detector using a total fiducial sensitivity of 1.56 kT yr. The atmospheric neutrino interaction sample has been compared to a Monte Carlo simulation which includes neutrino oscillations. The v e ( v e ) ∌v μ , ( v μ ), v e ( v e ) ∌v τ v μ ( v μ ) ∌v τ ( v τ) oscillations channels have been studied using the ratio of electron to muon charged current events. Three independent analyses have been performed and no evidence for neutrino oscillations has been found. The resulting limits on Δm2 for maximal mixing are more restrictive by more than one order of magnitude with respect to earlier measurements.

The Fréjus nucleon decay detector

Abstract The characteristics, trigger and monitoring systems, data acquisition as well as the performance of the Frejus nucleon decay detector are presented.

Search for neutron-antineutron oscillations in the Fréjus detector

Abstract From the analysis of the fully contained events recorded in the underground Frejus detector, a lower limit of 1.2×108s at 90% CL is derived for the free neutron-antineutron oscillation time.

Strange particle production and charmed particle search in the gargamelle neutrino experiment

Abstract Data is given for single and multiple strange particle production in neutrino reactions in both charged and neutral current channels. A total of 15000 neutrino and antineutrino events has been examined for possible evidence of semi-leptonic decay of a charmed particle. One candidate has been observed. Upper limits on charmed particle production cross-sections are given as a function of the neutrino energy and the invariant mass of the final state hadrons.

Analysis of Ke3+ decay

Abstract A study has been made of 2700 decays of the type K + → π o e + v in the CERN 1.1 m 3 heavy liquid bubble chamber. The four-momentum transfer dependence of the form factor f + ( q 2 ) has been determined. The usual linear parametrization f + ( q 2 ) = f + (0) (1+ λ + q 2 / m 2 π ) gives λ + = 0.027 ± 0.010.

Search for Muons from the Direction of Cygnus X-3

We have analyzed muons and multimuons detected in the Frejus underground nucleon decay detector between February 1984 and June 1986. No excess events are observed in the direction of Cygnus X-3, which yields a 90 % confidence level upper flux limit of 0.7 10-12 cm-2 s-1, for an average rock overburden of 5000 hg cm-2 corresponding to energies > 3 TeV. Using the 4.79 hour periodicity of Cygnus X-3, no signal is found in any phase interval.

Lifetime limits on (B-L)-violating nucleon decay and di-nucleon decay modes from the Fréjus experiment

The fully contained events recorded in the Frejus detector are used to search for (B-L)-violating nucleon decay and di-nucleon decay processes. No signal is found for a sensitivity of 2.0 kiloton year. The lower limits on the partial lifetime for the various nucleon decay modes range from 5.4×1030 yr for p→μ−π+K+ to 1.0×1032 yr for pn→e+n. We also quote limits on neutron and di-neutron decay into three and two neutrinos respectively.

Decay of the K0 meson into three pions: Test of CP conservation and ΔI = 12 non leptonic selection rule

Abstract CP invariance and ΔI= 1 2 rule are tested by analysing 136 K0→π+π-π0 and 54 of the type K0→π0π0π0 observed in a heavy liquid bubble chamber. There is no evidence against either hypothesis.

Neutral pion production by weak neutral currents in neutrino and antineutrino reactions

Abstract A study is presented of single πo production in neutrino and antineutrino interactions in Gargamelle filled with freon CF3Br. Limits on the neutral to charged current cross-section ratios R v =σ(v N →v N ′π o )/2 σ(v N → μ - N ′π o ) and R ν = σ( ν N → ν N ′π o )/2 σ( ν N → ω + N ′π o ) are found to be 0.10 ν and 0.26 ν at 68% confidence level.