80 research outputs found

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

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    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

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    Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

    The performance of the jet trigger for the ATLAS detector during 2011 data taking

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    The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4 % in the central region and better than 2.5 % in the forward direction

    Long-range Angular Correlations On The Near And Away Side In P-pb Collisions At √snn=5.02 Tev

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    7191/Mar294

    La numérotation des cahiers et la foliotation dans les manuscrits arabes datés jusqu'à 1450

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    Cette étude vise à établir une typologie de la façon dont sont numérotés les cahiers dans les manuscrits arabes, d'après les manuscrits conservés à la BNF, qui émanent de milieux très différents et ont été copiés dans les régions les plus diverses. La position de ces indications dans la page, les signes utilisés (alphabet abjad, chiffres de différents types, numérotation en toutes lettres), leur contenu – qui inclut parfois le numéro du feuillet dans le cahier ou encore le titre de l'ouvrage, ont varié avec le temps. On peut relever des pratiques particulières au Maghreb, où l'usage de la numérotation des cahiers a été moins fréquent ; dans les manuscrits chrétiens du Proche-Orient, où la foliotation apparaît relativement tôt, les pratiques doivent être mises en relation avec les traditions syriaque et copte. Dans les manuscrits scientifiques du Proche-Orient non caractérisés comme chrétiens, il semble avoir été fait un usage plus fréquent de l'alphabet abjadet des numérotations en chiffres. L'étude d'un plus grand nombre de manuscrits localisés devrait permettre par la suite de préciser ces données

    Practices and networks supporting the on-farm management of plant genetic resources for food and agriculture

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    Millions of farmers depend on the use of local crops and varieties for their food and livelihood. These resources constitute a reservoir of alternative traits and characteristics, which allow us to diversify crops, foods and farming methods and provide material for targeted plant breeding. Still, many countries lag behind in providing support to farming communities for the maintenance and use of plant genetic resources for food and agriculture (PGRFA). A global survey was conducted among a wide range of stakeholders to gain insights into the state of on-farm management (OFM) as a strategy for enhancing the maintenance and sustainable use of PGRFA. The survey showed that a wide range of stakeholders provide de facto support to OFM and that the practices they consider critical are focused on building capabilities in local communities. This supports the fact that the management of crop diversity on farm can be promoted in a variety of ways, depending on the specific context, and that local solutions are needed to successfully support OFM. Partnerships and networks should be considered as one of the critical means to promote OFM, as they involve a diversity of stakeholders working towards common goals. The survey further showed that many respondents currently contribute to existing networks relevant to OFM, but that these networks are mainly nationally or internationally oriented and might therefore exclude crucial local stakeholders, such as community-based organizations. Therefore, mechanisms should be put in place to strengthen the collaboration between stakeholders and networks, especially at the local level
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