[en] The final oscillation analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. Reconstruction algorithms of data extracted by electronic detectors were improved and the data recorded in the emulsion target were analysed by new automated scanning systems, allowing the use of a new method for event reconstruction in emulsion. CHORUS has applied these new techniques to the sample of 1996-1997 events for which no muons were observed in the electronic detectors. Combining the new sample with the data analysed in previous papers, the overall sensitivity of the experiment to the ν_τ appearance is thus improved. In a two-neutrino mixing scheme, a 90% C.L. upper limit of sin²2θ_μτ<4.4x10^-4 is set for large Δm², improving by a factor 1.5 the previously published CHORUS result

[en] We describe the (2x800 kg) emulsion target in the CHORUS hybrid detector set-up for the search of ν_μ→ν_τ oscillations, together with the CERN pouring and processing facilities (upgraded for this purpose), and the techniques employed to treat the emulsions used as the active target in the experiment

[en] We present a leading order QCD analysis of a sample of neutrino induced charged-current events with two muons in the final state originating in the lead-scintillating fibre calorimeter of the CHORUS detector. The results are based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign dimuon events collected during the exposure of the detector to the CERN Wide Band Neutrino Beam between 1995 and 1998. The analysis yields a value of the charm quark mass of m_c=(1.26±0.16±0.09)GeV/c² and a value of the ratio of the strange to non-strange sea in the nucleon of κ=0.33±0.05±0.05, improving the results obtained in similar analyses by previous experiments

[en] The nuclear emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy from 1994 to 1997. In total, about 100 000 charged-current (CC) neutrino interactions with at least one identified muon were located in the emulsion target and fully reconstructed, using newly developed automated scanning systems. Charmed particles were searched for by a program recognizing particle decays. The observation of the decay in nuclear emulsion makes it possible to select a sample with very low background and minimal kinematical bias. In all, 2013 CC interactions with a charmed hadron candidate in the final state were selected and confirmed through visual inspection. The charm production rate induced by neutrinos relative to the CC cross-section is measured to be σ(ν_μN→μ^-CX)/σ(CC)=(5.75 ± 0.32(stat)±0.30(syst))%. The charm production cross-section as a function of neutrino energy is also obtained. The results are in good agreement with previous measurements. The charm-quark hadronization produces the following charmed hadrons with relative fractions (in %): f_D⁰=43.7±4.5, f_Λc⁺=19.2±4.2, f_D⁺=25.3±4.2 and f_Ds⁺=11.8±4.7.

[en] The production and decay of a charmed particle has been observed in a γ induced reaction in nuclear emulsion. From a kinematical analysis of the decay, the flight time of the particle has been determined to be a few times 10^-13s. (Auth.)

[en] Two new examples of production by neutrinos and subsequent decay of charged charmed hadrons are reported. Together with two similar events reported previously they show that the lifetime of charged charmed particles is in the neighbourhood of 5 X 10^-13s, as expected from current theoretical models. One of the new events is identified as a baryon Λ⁺sub(c) of mass 2.295 +- 0.015 GeV/c² which undergoes the decay process Λ⁺sub(c) → pπ⁺K^- with a proper decay time (7.3 +- 0.1) X 10^-13 s. (Auth.)

[en] The final results from the CHARM II experiment on neutrino-electron scattering and inverse muon decay (IMD) are reported. From the study of the first process the vector and axial-vector coupling constants of the muon neutrino to the electron, g_V^νe, are obtained; the comparison of these results with the LEP measurements allows to test the Standard Model at a scale of Q² ∼0.01 GeV²,to estimate the coupling of the muon neutrino to the Z, and to test the universality of neutrino couplings in neutral current interactions. The study of the inverse muon decay reaction complements the results on muon decay in determining the structure of the charged current coupling of the electron to the muon; a limit on the scalar coupling of these particles is derived. (author). 5 figs., 9 refs

[en] A search for ν_μ → ν_e and anti ν_μ → anti ν_e oscillations has been carried out with the CHARM II detector exposed to the CERN wide band neutrino beam. The data were collected over five years, alternating beams mainly composed of muon-neutrinos and muon-antineutrinos. The number of interactions of ν_e and anti ν_e observed is comparable with the number of events expected from flux calculations. For large squared mass differences the upper limits obtained on the mixing angle are sin²2θ < 9.4 . 10^-3 for ν_μ oscillating to ν_e and sin²2θ < 4.8 . 10^-3 for anti ν_μ to anti ν_e, at the 90% confidence level. Combining neutrino and antineutrino data the upper limit is 5.6 . 10^-3. (orig.)

[en] New results on inverse muon decay and coherent charged pion production by neutrinos are presented. The data come from the CHARM-II neutrino detector operated at the CERN wide-band neutrino beam. High-statistics data samples of 14500 inverse muon decay events and 3500 ν_μe elastic scattering events allow the determination of the electroweak parameters from the ratio of the cross-sections of neutral-to-charged-current neutrino electron scattering. The best fit values of the electroweak mixing angle sin² θ_W and the relative coupling strength ρ of neutral and charged current are: sin² θ_W = 0.237±0.014 and ρ = 0.987±0.042. In the second topic, coherent single charged pion production was measured in neutrino and antineutrino beams. The measured cross-sections, averaged over the wide-band beam spectra and the glass target nuclei composition, are: σ(ν_μA → μ^-π⁺A) = (51±10) x 10^-40 cm² nucleus and σ( anti ν_μA → μ⁺π^-A) = (43±9) x 10^-40 cm² nucleus. The energy dependence shows the expected flattering of the cross-sections at high energy. (orig.)

[en] We are reporting on a determination of neutral current coupling constants from a study of differential cross sections of muon-(anti)neutrino electron scattering. The results were obtained with the CHARM-II detector which was exposed to the CERN wide band neutrino beam in the years 1987 to 1991. A total of about 3000 νe and 3000 anti νe scattering events were observed. We present a preliminary value of sin² θ_W determined with the ratio of neutrino and antineutrino electron scattering cross-sections, based on the full data sample, and we give a determination of the effective vector and axial-vector neutral current coupling constants and the first measurement of the shape of the y-distributions based on 80% of the total statistics. (orig.)