No abstract available

No abstract available

[en] During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS collecting about 10⁶ neutrino interactions. A measurement of ν-bar _μ-induced charm production is performed by using the presence of a 5% ν-bar _μ component in the ν_μ beam. The measurement takes advantage of the capability to observe the decay topology in the emulsion. The analysis is based on a sample of charged-current interactions with at least one identified muon. About 100-bar 000 were located in the emulsion target and fully reconstructed. By requiring a positive muon charge as determined by the CHORUS muon spectrometer, 32ν-bar _μ-induced charm events were observed with an estimated background of 3.2 events. At an average antineutrino energy in the neutrino beam of 18 GeV, the charm production rate induced by antineutrinos is measured to be σ(ν-bar _μN->μ⁺c-bar X)/σ(ν-bar _μN->μ⁺X)=(5.0_-0.9^+1.4(stat)+/-0.7(syst))%. The ratio between neutral and charged charm production rates in this process is (2.6_-1.0^+1.7(stat)+/-0.8(syst)). The charm production rate as a function of the antineutrino energy is found to be in good agreement with previous results derived from di-lepton data

[en] During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS. In total about 100-bar 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events which was based on the data acquired by new automatic scanning systems, 1048 D⁰ events were selected by a pattern recognition program. They were confirmed as neutral-particle decays through visual inspection. Fragmentation properties of deep-inelastic charm production were measured using these events. Distributions of the D⁰ momentum, Feynman x (x_F), z and tanθ^out, the transverse angle out of the leptonic plane defined by the muon and the neutrino, are presented. The mean value of z was measured to be < z>=0.63+/-0.03(stat)+/-0.01(syst). From fits to the z distribution, values for the Peterson parameter ε_P=0.108+/-0.017(stat)+/-0.013(syst) and the Collins-Spiller parameter ε_CS=0.21_-0.04^+0.05(stat)+/-0.04(syst) are found. For the average value of x_F we find < x_F>=0.38+/-0.04(stat)+/-0.03(syst) and for the forward-backward asymmetry A=0.79+/-0.14(stat)+/-0.05(syst). The distribution of tanθ^out was measured with an average value < tanθ^out>=0.030+/-0.002

[en] The CHORUS experiment, designed to search for ν_μ→ν_τ oscillations, consists of a nuclear emulsion target and electronic detectors. In this paper, results on the production of charged particles in a small sample of charged-current neutrino- and anti-neutrino-nucleus interactions at high energy are presented. For each event, the emission angle and the ionization features of the charged particles produced in the interaction are recorded, while the standard kinematic variables are reconstructed using the electronic detectors. The average multiplicities for charged tracks, the pseudo-rapidity distributions, the dispersion in the multiplicity of charged particles and the KNO scaling are studied in different kinematical regions. A study of quasi-elastic topologies performed for the first time in nuclear emulsions is also reported. The results are presented in a form suitable for use in the validation of Monte Carlo generators of neutrino-nucleus interactions. (orig.)

[en] A systematic search for superfragments (charmed nuclei) has been performed in 22 200 neutrino-emulsion interactions obtained with the CHORUS experiment making use of automatic off-line image analysis. The absence of candidates provides an upper limit for the superfragment production rate of 1.9x10^-4 (90% C.L.) relative to neutrino charged-current interactions at an average neutrino energy of 27 GeV. In the same analysis 28 hyperfragment decays were found. For the first time, a production rate of hyperfragments in neutrino-emulsion interactions was obtained. The value of the hyperfragment production rate relative to the neutrino charged-current cross-section was found to be (2.0±0.4(stat)±0.3(syst))x10^-3

[en] During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy. In total about 100-bar 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events which was based on the data acquired by new automatic scanning systems, 1048 charged-current interactions with a D⁰ in the final state were selected by a pattern recognition program and confirmed as neutral-particle decays through visual inspection. The ratio of decay branching fractions of the D⁰ into four charged particles to two charged particles was measured to be B(D⁰->V4)/B(D⁰->V2)=0.207+/-0.016+/-0.004. The inclusive measurement of the observed production rate of the D⁰ with a decay into four charged prongs in combination with external measurements of this topological branching ratio was used to determine the total D⁰ production rate by neutrinos without additional assumption on the branching fractions. The value of this rate relative to the charged-current cross-section was found to be σ(D⁰)/σ(CC)=0.0269+/-0.0018+/-0.0013. In addition, the same normalization method was used to deduce the inclusive topological decay rate into final states with neutral particles only. A value of 0.218+/-0.049+/-0.036 was found for this branching fraction. From an observed number of three charged six-prong events the branching ratio into six charged particles was determined to be (1.2_-0.9^+1.3+/-0.2)x10^-3. A measurement of the energy dependence of the D⁰ production by neutrinos relative to the total charged-current cross-section is also reported. This measurement was used to deduce for m_c, the effective charm-quark mass, a value of (1.42+/-0.08)GeV/c²

[en] The experiments at the Large Hadron Collider (LHC) will have to deal with unprecedented radiation levels. In the large-rapidity regions, close to the beam pipe, these levels reach megagrays per year. The detectors to be installed in these regions, the HF Calorimeters, are designed to operate under these conditions. In this paper, we describe the results of studies in which a prototype calorimeter was exposed to radiation of the type and intensity expected at the LHC. These studies made it possible to estimate the effects of this radiation on the response and the resolution of the calorimeter as a function of time during LHC operation

[en] During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy. In total about 100-bar 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. A high-statistics sample of neutrino interactions with a D⁰ in the final state was collected. Using the decay mode D*⁺->D⁰π⁺ a production cross-section measurement of the D*⁺ in neutrino-nucleon charged-current interactions was performed. The low Q-value of the decay was used to isolate a sample of candidate events containing a positive hadron with a small p_T with respect to the D⁰ direction. A signal of 22.1+/-5.5D*⁺ events was obtained. The D*⁺ production cross-section relative to the D⁰ production cross-section, σ(D*⁺)/σ(D⁰), was estimated to be 0.38+/-0.09(stat)+/-0.05(syst). From this result, the fraction of D⁰'s produced via the decay of a D* was deduced to be 0.63+/-0.17. The D*⁺ production cross-section relative to the ν_μ charged-current interaction, σ(D*⁺)/σ(CC), was estimated to be [1.02+/-0.25(stat)+/-0.15(syst)]%

[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.