[en] The NOMAD experiment has been searching for ν_μ ↔ ν_τ oscillations by looking for the appearance of τ^- in events from the CERN-SPS neutrino beam. With some improvements in the analysis techniques with respect to the previous published results and including data from 1995 to 1997, no evidence for oscillations is found, resulting in an updated limit in the oscillation probability of P(ν_μ ↔ ν_τ) < 0.6 x 10^-3 at 90% C.L. This corresponds to a limit on the oscillation mixing angle of sin² 2Θ_μτ < 1.2 x 10^-3 for large Δm²

[en] The dijet cross section in photoproduction has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb^-1. The events were required to have a virtuality of the incoming photon, Q², of less than 1 GeV² and a photon-proton centre-of-mass energy in the range 134 < W_γp < 277 GeV. Each event contains at least two jets satisfying transverse-energy requirements of E^jet1_T > 14 GeV and E^jet2_T > 11 GeV and pseudorapidity requirements of -1 < η^jet1,2 < 2.4. The measurements are compared to next-to-leading-order QCD predictions. The data show particular sensitivity to the density of partons in the photon, allowing the validity of the current parameterizations to be tested. (author)

[en] Respiratory gated PET/CT (positron emission tomography/computed tomography) of the lung is expected to increase the accuracy of quantitative determinations in lesional activities, regardless of the gating method used; reasonably, respiratory gating should increase standard uptake value (SUV; and possibly decrease lesional size), on the basis of the reduction of the smearing effect.'' However, literature data are very limited, particularly for in vivo studies. The objective of this article is to test the SUV variations in a large group of lung lesion studies. A group of 26 consecutive positive studies (21 men, 5 women, age 36-84, mean 68), performed on patients referred to our institution for known or suspected lung cancer, are examined. All studies were performed both with conventional PET/CT total body scan and with Real-Time Position Management (RPM) triggered selective gated study of the thorax. Four studies were considered technically unsatisfactory and were discarded; the remaining 22 studies are the object of this work. Max lesional SUVs were evaluated in both settings by semi-automated algorithms; for the gated studies, both values of the bin that showed more relevant variations from the clinical routinary study (''best bin'') and an average value that was calculated over all bins were determined. Results were compared on a one-to-one basis. In conventional, SUV showed a mean±standard deviation (SD) value of 9.2±6.9 (range 0.9-26). In the averaged gated studies, the mean±SD value was 13.4±11.7 (range 1.4-47); in the ''best bin'' dataset the mean±SD was 14.9±12.9, ranging from 1.6 to 53.1. In general, the use of respiratory trigger induced rather variable but overall consistent increases in SUV. If the percentage variations in the average trigger dataset are considered, there is an average increase of +60%, SD ±97 (P<0.05). Similar results are found in the ''best bin'' dataset, the average percentage increase in SUV values being +77.2% (SD±04.6). In lung cancer, triggering procedures increase the signal to noise ratio. The increase in SUV determined by gating is very variable, but generally relevant. This could lead to an SUV values cut-off revision, and may have an impact on smaller lesions detection. (author)

[en] In this paper we present a study of the signal produced by electrons and pions of energies ranging between 1 GeV and 180 GeV in modules of ATLAS Tile Calorimeter. Results are compared to Geant4 simulation by analyzing linearity, resolution, e/π ratio and shower profile. The final goal is to tune and validate, in the simple Test Beam geometry, the Geant4 simulation program

[en] The precision of the final jet energy scale is a fundamental ingredient for important physics measurements, like the top-quark mass, or even for new discoveries (SUSY). The ATLAS calorimeter requirements in terms of uniformity and resolution have been achieved and verified in many years of tests on beam at CERN. The key issues for the jet reconstruction and calibration in ATLAS (agreement between test beam data and the Geant 4 predictions, clustering strategies, reconstruction and calibration algorithms) will be briefly discussed and reviewed

[en] Four surface reflectance models of solar radiation were determined by examining several sets of field measurements taken for clear-sky conditions at various sites in Antarctica. Each model consists of the mean spectral curve of surface reflectance in the 0.25-2.7 μm wavelength range and of the dependence curve of total abedo on the solar elevation angle h, within the range from 5⁰ to 55⁰. The TNB (Terra Nova Bay) model refers to a rocky terrain where granites are predominant; the NIS (Nansen Ice Sheet) model to a glacier surface made uneven by sastrugi and streaked by irregular fractures; the HAP (High Altitude Plateau) model to a flat ice surface covered by fresh snow and scored by light sastrugi; and the RIS (Ross Ice Shelf) model to an area covered by the sea ice pack presenting many discontinuities in the reflectance features, due to melt water lakes, puddles, refrozen ice and snow pots. The reflectance curve obtained for the TNB model presents gradually increasing values as wavelength increases through the visible spectral range and almost constant values at infrared wavelengths, giving a total albedo value equal to 0.264 at = 30⁰, which increases by about 80% through the lower range of h and decreases by 12% through the upper range. The reflectance curves of the NIS, HAP and RIS models are all peaked at visible wavelengths and exhibit decreasing values throughout the infrared spectral range, giving values of total albedo equal to 0.464, 0.738 and 0.426 at h 30⁰, respectively. These values were estimated to increase by 8-14% as h decreases from 30⁰ to 5⁰ and to decrease by 2-4% only as h increases from 30⁰ to 55⁰

[en] The NOMAD-STAR detector is a silicon vertex detector installed in the NOMAD spectrometer at the CERN SPS neutrino beam. It consists of four layers of a passive boron carbide target with a total mass of 45 kg and five layers of 600 single-sided silicon microstrip detectors covering a total area of 1.14 m². About 11,500ν_μ charged current interactions were reconstructed in the fiducial volume of NOMAD-STAR from the neutrino run in 1998. The potential use of silicon detectors for ν_μ(ν_e)↔ν_τ oscillations depends on the observation of the τ candidates by the experimental signature of a large impact parameter, in the case of the one prong decay of the τ, or a double vertex, in the case of the three prong decay. The main aim of NOMAD-STAR is to measure the impact parameter and vertex distributions of charged current interactions, which constitute the main backgrounds for the oscillation signals, to understand the significance of a potential signal in a future experiment. The present paper describes the experience gained in the operation of this silicon vertex detector, and the performance achieved with it

[en] A description of the response of the NOMAD electromagnetic calorimeter to electrons and photons is discussed. In particular, the dependence of the two-dimensional shower shape on the angle and energy of the incident particle is parametrized by analytical functions. Some applications to the neutrino event reconstruction are also reported

[en] Test beam results of the NOMAD electromagnetic calorimeter are presented showing linearity, signal uniformity, energy and position resolution measured in an electron beam. Tests were also performed placing the calorimeter in a magnetic field of 0.4 T. Results on the π rejection obtained using a combined measurement of preshower/electromagnetic calorimeter are found to be in good agreement with the project expectations. Finally the calorimeter response to the muons is discussed. (orig.)

[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