[en] The mass of the charm quark, the V_cd matrix element, the impulse distribution s(x) of the proton strange quark can be measured by the events producing lepton pairs during neutrino-matter interactions. This study has been done with CCFR and will be performed with NOMAD (Neutrino Oscillation Magnetic Detector)

[en] We present a measurement of the polarization of Λ-bar hyperons produced in ν_μ charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V⁰ identification procedure and analysis method reported in a previous paper [NOMAD Collaboration, Nucl. Phys. B 588 (2000) 3] for the case of Λ hyperons. The Λ-bar polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero

[en] The inclusive production of the meson resonances ρ⁰(770), f₀(980) and f₂(1270) in neutrino-nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the f₀(980) meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of f₂(1270) in neutrino interactions is reliably established. The average multiplicity of these three resonances is measured as a function of several kinematic variables. The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model. In addition, the average multiplicity of ρ⁰(770) in antineutrino-nucleus interactions is measured

[en] The Λ polarization in ν_μ charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Λ 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the W -boson direction which is enhanced in the target fragmentation region: P_x(x_F<0)=-0.21±0.04(stat)±0.02(sys) . In the current fragmentation region we find P_x(x_F>0)=-0.09±0.06(stat)±0.03(sys) . These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the Λ production plane) has been observed for the first time in a neutrino experiment: P_y=-0.22±0.03(stat)±0.01(sys) . The dependence of the absolute value of P_y on the Λ transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron-hadron experiments

[en] Results from the ν_τ appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic τ decays, significantly improving the overall sensitivity of the experiment to oscillations. The 'blind analysis' of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% CL allowed region in the sin²2θ_μτ-Δm² plane which includes sin²2θ_μτ<3.3x10^-4 at large Δm² and Δm²< 0.7 eV²/c⁴ at sin²2θ_μτ=1. The corresponding contour in the ν_e→ν_τ oscillation hypothesis results in sin²2θ_eτ<1.5x10^-2 at large Δm² and Δm²<5.9 eV²/c⁴ at sin²2θ_eτ=1. We also derive limits on effective couplings of the τ lepton to ν_μ or ν_e

[en] Bose-Einstein correlations in one and two dimensions have been studied, with high statistics, in charged current muon-neutrino interaction events collected with the NOMAD detector at CERN. In one dimension the Bose-Einstein effect has been analyzed with the Goldhaber and the Kopylov-Podgoretskii phenomenological parametrizations. The Goldhaber parametrization gives the radius of the pion emission region R_G=1.01±0.05(stat)^+0.09_-0.06(sys) fm and for the chaoticity parameter the value λ=0.40±0.03(stat)^+0.01_-0.06(sys). Using the Kopylov-Podgoretskii parametrization yields R_KP=2.07±0.04(stat)^+0.01_-0.14(sys) fm and λ_KP=0.29±0.06(stat)^+0.01_-0.04(sys). Different parametrizations of the long-range correlations have been also studied. The two-dimensional shape of the source has been investigated in the longitudinal comoving frame. A significant difference between the transverse and the longitudinal dimensions is observed. The high statistics of the collected sample allowed the study of the Bose-Einstein correlations as a function of rapidity, charged particle multiplicity and hadronic energy. A weak dependence of both radius and chaoticity on multiplicity and hadronic energy is found

[en] Backward proton and π^- production has been studied in ν_μ CC interactions with carbon nuclei. Detailed analyses of the momentum distributions, of the production rates, and of the general features of events with a backward going particle, have been carried out in order to understand the mechanism producing these particles. The backward proton data have been compared with the predictions of the reinteraction and the short range correlation models

[en] The method developed for the calculation of the flux and composition of the West Area Neutrino Beam used by NOMAD in its search for neutrino oscillations is described. The calculation is based on particle production rates computed using a recent version of FLUKA and modified to take into account the cross-sections measured by the SPY and NA20 experiments. These particles are propagated through the beam line taking into account the material and magnetic fields they traverse. The neutrinos produced through their decays are tracked to the NOMAD detector. The fluxes of the four neutrino flavours at NOMAD are predicted with an uncertainty of about 8% for ν_μ and ν_e, 10% for ν-bar_μ, and 12% for ν-bar_e. The energy-dependent uncertainty achieved on the ν_e/ν_μ prediction needed for a ν_μ→ν_e oscillation search ranges from 4% to 7%, whereas the overall normalization uncertainty on this ratio is 4.2%

[en] A study of strange particle production in ν_μ charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles (K⁰_s,Λ,Λ-bar) have been measured. Mean multiplicities are reported as a function of the event kinematic variables E_ν, W² and Q² as well as of the variables describing particle behaviour within a hadronic jet: x_F, z and p_T². Decays of resonances and heavy hyperons with identified K⁰_s and Λ in the final state have been analyzed. Clear signals corresponding to K^*±, Σ^*±, Ξ^- and Σ⁰ have been observed

[en] We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions (ν_μn →μ^-p and anti ν_μp→μ⁺n) using a set of experimental data collected by the NOMAD Collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly carbon) normalizing it to the total ν_μ(anti ν_μ) charged-current cross section. The results for the flux-averaged QEL cross sections in the (anti)neutrino energy interval 3-100 GeV are left angle σ_qel right angle _νμ=(0.92±0.02(stat)±0.06(syst)) x 10^-38 cm² and left angle σ_qel right angle _antiνμ=(0.81±0.05(stat)±0.09(syst)) x 10^-38 cm² for neutrino and antineutrino, respectively. The axial mass parameter M_A was extracted from the measured quasi-elastic neutrino cross section. The corresponding result is M_A=1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross section and extracted from the pure Q² shape analysis of the high purity sample of ν_μ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured M_A is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of M_A is lower than those recently published by K2K and MiniBooNE Collaborations. However, within the large errors quoted by these experiments on M_A, these results are compatible with the more precise NOMAD value. (orig.)