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The ATLAS detector has been built to study the reactions produced by the Large Hadron Collider (LHC). ATLAS includes a system of liquid argon calorimeters for energy measurements. The electronics for amplifying, shaping, sampling, pipelining, and digitizing the calorimeter signals is implemented on a set of front-end electronic boards. The front-end boards are installed in crates mounted between the calorimeters, where they will be subjected to significant levels of radiation during LHC operation. As a result, all components used on the front-end boards had to be subjected to an extensive set of radiation qualification tests. This paper describes radiationtolerant designs, radiation testing, and radiation qualification of the front-end readout system for the ATLAS liquid argon calorimeters.
We present the results of a search for nu_mu → nu_e oscillations in the NOMAD experiment at Cern. The experiment looked for the appearance of nu_e in a predominantly nu_mu wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are Delta m^2 < 0.4 eV^2 for maximal mixing and sin^2(2theta) < 1.4 X 10^-3 for large Delta m^2. This result excludes the LSND allowed region of oscillation parameters with Delta m^2 >~ 10 eV^2.
A study of strange particle production in nu(mu) charged cur- rent interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles (K-S(0), Lambda, (Λ) over bar) have been measured. Mean multiplicities are reported as a function of the event kinematic variables E-nu W-2 and Q(2) as well as of the variables describing particle behaviour within a hadronic jet: x(F), z and p(T)(2). Decays of resonances and heavy hyperons with identified K, and A in the final state have been analyzed. Clear signals corresponding to K*+/-, Sigma(*+/-), Xi(-) and Sigma(0) have been observed.
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 interacti...
Backward proton and pi (-) production has been studied in nu (mu) 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.
Results from the v, appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic tau 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 sin(2)2 theta (mu tau)-Deltam(2) plane which includes sin(2)2 theta (mu tau) lt 3.3 x 10(-4) at large Deltam(2) and Deltam(2) lt 0.7 eV(2)/c(4) at sin(2) 2 theta (mu tau) = 1. The corresponding contour in the nu (e) → nu (tau) oscillation hypothesis results in sin(2) 2 theta (l tau) lt 1.5 x 10(-2) at large Deltam(2) and Deltam(2) lt 5.9 eV(2)/c(4) at sin(2) 2 theta (l tau) = 1. We also derive limits on effective couplings of the ...
The NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of leading order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with E/sub mu 1/,E/sub mu 2/ gt 4.5 GeV, 15 lt E/sub nu / lt 300 GeV and Q/sup 2/ gt 1 (GeV/c)/sup 2/ are observed in the front-calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of m/sub c/=1.3/sub -0.3-0.3//sup +0.3+0.3/ GeV/c/sup 2/ and for the average semileptonic branching ratio of B/sub c/=0.095/sub -0.007-0.013//sup +0.007+0.014/. The ratio of the strange to non-strange sea in the nucleon is measured to be kappa =0.48/sub -0.07-0.12//sup +0.09+0.17/. The measured rate of charm-induced dimuon relative to single muon, as a function of neutrino energy, is consistent with the slow rescalin...
We report on a search for heavy neutrinos ( nu /sub 4/) produced in the decay D/sub s/ to tau nu /sub 4/ at the SPS proton target followed by the decay nu /sub 4/ to nu /sub tau /e/sup +/e/sup -/ in the NOMAD detector. Both decays are expected to occur if nu /sub 4/ is a component of nu /sub tau /. From the analysis of the data collected during the 1996-1998 runs with 4.1*10/sup 19/ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the nu /sub 4/ mass range from 10 to 190 MeV. Windows between the SN1987 A and big bang nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time a...
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