[en] In the Gosgen oscillation experiment flux and energy spectrum of these electron antineutrinos were monitored at two distances from the reactor core (37.9 m, 45.9 m). The detector system, well shielded against cosmic radiation, is based on the detection reaction upsilonsub(e)sup(c) + p->n + esup(*) and an alternating array of liquid scintillators and He wire chambers serves as positron and neutron detectors. As signature for a good event a time and position correlation of the detected neutron and positron is required. In addition the measured position energy spectrum directly reflects the incident neutrino energies. To analyze the data in terms of oscillations, either the spectra measured in each position are compared to theoretical predictions for different oscillation parameters or a relative comparison of both measurements is performed. Allowing in the analysis a variation of 2 standard deviations for the systematic uncertainties the following limits on the oscillation parameters are obtained in a combination of the data from both measuring positions: mixing angle: [large mass param.] sin² 20 < 0.24 (90% c.l.), mass param.: [maximum mixing] Δ m² < 0.02 (eV)² (90% c.l.). (orig./HSI)

No abstract available

[en] In this paper the recent result for the weak mixing angle sin²Θ_W, determined in neutrino electron scattering by the CHARM II collaboration at the CERN SPS is reported. From the ratio of ν_μe to ν_μe scattering cross sections a value of sin²Θ_W = 0.233 ± 0.012(stat) ± 0.008(syst) was determined

No abstract available

[en] One of the most challenging problems in todays physics remains the question, whether the neutrino possesses a finite restmass. Experiments searching for neutrino oscillations provide important information on neutrino masses and on the possibility of mixing of different neutrino states. In this paper the principles of a neutrino oscillation experiment at a nuclear power reactor are described and the latest results are presented. (orig.)

[en] A new detector technique based on scintillating optical fibers with 100 μm to 200 μm diameter is proposed for the use in neutrino physics. These detectors can be realized with large fiducial masses and have an excellent spatial resolution, good energy and time resolving capabilities. The application of this detector concept for the search of ββ-decay, the measurement of the magnetic moment of the neutrino and for an improved search for ν_μ → ν_τ oscillations is discussed. (author) 4 refs., 1 fig

[en] A search for neutrino oscillations has been conducted at the 2800-MW (thermal) nuclear power reactor in Goesgen (Switzerland), providing 5 x 10/sup 20/ electron antineutrinos per second. The energy spectrum of the antineutrinos was measured at three distances, 37.9, 45.9, and 64.7 m, from the reactor core. The detection of the neutrinos is based on the reaction nu-bar/sub e/+p→e⁺+n. Roughly 10⁴ antineutrinos were registered at each of the three measuring positions. The measured spectra are analyzed in terms of a two-neutrino oscillation model and the results are represented as exclusion plots for the oscillation parameters Δm² and sin²2theta. Two analyses are performed: Analysis A relies exclusively on the data measured at the three different distances; analysis B combines the measured data with additional information, in particular with the reactor antineutrino spectrum as derived from independent β-spectroscopic measurements. Both analyses show that the data are consistent with the absence of neutrino oscillations, and rule out large regions of parameters (Δm²,theta). The resulting limits on the oscillation parameters are Δm²<0.019 eV² (90% C.L.) for maximum mixing and sin²2theta<0.21 (90% C.L.) for Δm²>5 eV²

[en] In this paper, the authors report on a new determination of sin²θ_w from the ratio of ν_μe to bar ν_μe scattering cross sections. 762 ν_mue and 1017 bar ν_μe have been observed in the 1987 and 1988 exposure of the CHARM II detector to the Wide Band Beam of the 450 GeV CERN SPS. From the ratio of cross sections the authors determined sin²θ⁰ = 0.233 ± 0.012(stat) ± 0.008(syst) without radiative corrections. With radiative corrections for m_t = m_H = 100 GeV the authors find sin²θ_w = 0.232 ± 0.012(stat) ± 0.008(syst)

[en] The positron spectrum from the reaction anti νsub(e) + p → e⁺ + n has been measured at L = 37.9 from the core of the Goesgen power reactor to search for neutrino oscillations of the type anti νsub(e)reversible x in the low mass parameter range. The results are consistent with the no neutrino oscillation hypothesis. Upper limits of Δm² <= 0.016 eV² (90% c.l.) for full mixing, and sin² 2THETA <= 0.17 (90% c.l.) in the limit of large mass parameters were determined. For the ratio of the integrated experimental yield to that prediced for the case of no oscillations a value of 1.05 +- 0.02 (statistical) +- 0.05 (systematik; 68% c.l.) was obtained. (orig.)

[en] The positron spectrum from the reaction anti νsub(e) + p -> e⁺ + n has been measured at L = 45.9 m from the core of the Goesgen power reactor. The data, combined with those of our previous measurement at 37.9 m, are analysed in terms of two-neutrino oscillations of the type anti νsub(e) <--> x. This analysis is essentially independent of external data on the spectral distribution of reactor neutrinos. No evidence for neutrino oscillations was found. A comprehensive analysis uncluding data on the spectral distribution yields upper limits for the oscillation parameters of Δm² <= 0.016 eV² (90% CL) for full mixing, and sin²2theta <= 0.16 (90% CL) for large Δm². (orig.)