Section efficace de la réaction 16O(t, n) 18F application au dosage de l'oxygène

Des échantillons de tantale oxydés anodiquement ont été irradiés avec des tritons de 1,6 à 3,7 MeV. La section efficace a été déterminée par mesure de la radioactivité du 18F. La valeur trouvée à 2 MeV est de 220 mb. Nos résultats sont en désaccord avec les valeurs publiées par Jarmie jusqu'à 2,2 MeV et avec la forme de la courbe obtenue par Barrandon et Albert entre 2 et 3 MeV. La réaction 16O(t, n) 18F a été utilisée pour doser l'oxygène à la surface d'échantillons d'acier inoxydable. Une limite de détection de 0,004 μg.cm-2 a été obtenue à 2 MeV, après 10 min. d'irradiation avec un faisceau de 0,2 μA de tritons. Les possibilités d'application aux dosages dans la masse sont discutées

Technical design and performance of the NEMO3 detector

The development of the NEMO3 detector, which is now running in the Frejus Underground Laboratory (L.S.M. Laboratoire Souterrain de Modane), was begun more than ten years ago. The NEMO3 detector uses a tracking-calorimeter technique in order to investigate double beta decay processes for several isotopes. The technical description of the detector is followed by the presentation of its performance.Comment: Preprint submitted to Nucl. Instrum. Methods A Corresponding author: Corinne Augier ([email protected]

Study of 2b-decay of Mo-100 and Se-82 using the NEMO3 detector

After analysis of 5797 h of data from the detector NEMO3, new limits on neutrinoless double beta decay of Mo-100 (T_{1/2} > 3.1 10^{23} y, 90% CL) and Se-82 (T_{1/2} > 1.4 10^{23} y, 90% CL) have been obtained. The corresponding limits on the effective majorana neutrino mass are: m < (0.8-1.2) eV and m < (1.5-3.1) eV, respectively. Also the limits on double-beta decay with Majoron emission are: T_{1/2} > 1.4 10^{22} y (90% CL) for Mo-100 and T_{1/2}> 1.2 10^{22} y (90%CL) for Se-82. Corresponding bounds on the Majoron-neutrino coupling constant are g < (0.5-0.9) 10^{-4} and < (0.7-1.6) 10^{-4}. Two-neutrino 2b-decay half-lives have been measured with a high accuracy, T_{1/2} Mo-100 = [7.68 +- 0.02(stat) +- 0.54(syst) ] 10^{18} y and T_{1/2} Se-82 = [10.3 +- 0.3(stat) +- 0.7(syst) ] 10^{19} y.Comment: 5 pages, 4 figure

Study of 2 beta-decay of Mo-100 and Se-82 using the NEMO3 detector

After analysis of 5797 h of data from the detector NEMO3, new limits on neutrinoless double beta decay of Mo-100 (T-1/2 > 3.1 x 10(23) y, 90% CL) and Se-82 (T-1/2 > 1.4 x 10(23) y, 90% CL) have been obtained. The corresponding limits on the effective majorana neutrino mass are: 1.4 x 10(22) y (90% CL) for Mo-100 and T-1/2 > 1.2 x 10(22) y (90% CL) for Se-82. Corresponding bounds on the Majoron-neutrino coupling constant are < (0.5-0.9) x 10(- 4) and <(0.7-1.6) x 10(- 4). Two-neutrino 2beta-decay half-lives have been measured with a high accuracy, (T1/2Mo)-Mo-100 = [7.68 +/- 0.02(stat) +/- 0.54(syst)] x 10(18) y and (T1/2Se)-Se-82 = [10.3 +/- 0.3(stat) +/- 0.7(syst)] x 10(19) y. (C) 2004 MAIK "Nauka/Interperiodica"

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Director Characteristics and Firm Performance

The traditional methodology examining optimal boards relates a simple board variable (e.g. independence or board demography) to firm performance, however, ig- noring other board characteristics. This paper investigates how the education and business experience of directors affect firm performance. The sample consists of 1,574 directorships from 224 listed firms in Switzerland. Using OLS and including control variables, the results show that graduates of minor Swiss universities are negatively related to Tobin’s Q, and industrial knowledge and Tobin’s Q are nega- tively correlated if the firm has more divisions. In addition, director fixed effects (or unobserved characteristics) are significant, but improve the explanatory power of the models only by 5 percent

Corporate boards and the performance of Asian firms: A meta-analysis

The prevalence of ownership concentration in Asian firms presents a challenge to the influential agency theory-based understanding of the role of corporate boards. In this paper we develop and test hypotheses about board attributes and firm performance that reflect Asian institutional conditions. We present the first meta-analysis of the relationship between board attributes and performance of Asian firms using a varied set of meta-analytical techniques on a database of 86 studies covering nine Asian countries. First, we find that board structure and composition preferences are influenced by the identity of the concentrated owner. Second, consistent with US data, we find very limited evidence of a direct relationship between board attributes and firm financial performance in the Asian context. Third, we find that the relationship between board structure and composition and firm performance is mediated by the revealed strategic preferences of Asian firms specifically by the level of R&D investment

Measurement of the Higgs boson mass in the H→ZZ ∗ →4ℓ and H→γγ channels with √s =13 TeV pp collisions using the ATLAS detector

The mass of the Higgs boson is measured in the H→ZZ ∗ →4ℓ and in the H→γγ decay channels with 36.1 fb −1 of proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The measured value in the H→ZZ ∗ →4ℓ channel is m ZZ ∗ H =124.79±0.37 GeV, while the measured value in the H→γγ channel is m γγ H =124.93±0.40 GeV. Combining these results with the ATLAS measurement based on 7 TeV and 8 TeV proton-proton collision data yields a Higgs boson mass of m H =124.97±0.24 GeV