3,425 research outputs found

    Top quark charge asymmetry measurements with ATLAS detector

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    The top quark charge asymmetry measurements performed with ATLAS detector at a centre-of-mass energy of 7 TeV are presented.Comment: 5 pages text + 1 title page , 4 figures Proceedings of the 8th International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna, Austria, September 8-12, 201

    Telling the spin of the "Higgs boson" at the LHC

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    We assume that the Higgs boson or a possible resonance---playing its role in strongly interacting models of electroweak symmetry breaking---has been discovered at the LHC and propose a search strategy to determine its spin based on two simple asymmetries in the ZZ, W+W- and t t-bar decays channels. We consider some benchmark values for its mass (in the interval from 182 GeV/c^2 to 1 TeV/c^2) and discuss the relative advantages of the different decay processes. A full analysis, including the background, is given. For a center-of-mass energy of 14 TeV, we find that the lowest integrated luminosity required to discriminate between the different spins is, depending on the process and the resonance mass, between 40 fb^{-1} and 250 fb^{-1}.Comment: 17 pages, 3 figure

    Supersymmetry searches with ATLAS detector at LHC

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    In this paper a brief overview of the principal strategies for Supersymmetry searches with ATLAS detector at LHC is presented. The aim is to evaluate the ATLAS discovery potential within mSUGRA parameter space of Supersymmetry, both in inclusive and exclusive channels, and to estimate the achievable precision in SUSY parameters in relation to the integrated luminosity available at LHC

    Measurement of SUSY parameters using events with dileptons with ATLAS

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    A review of some of the exclusive measurements of the SUSY masses and parameters using the reconstruction of events with 2 leptons+missing energy+jets with the ATLAS detector is presented

    Early Supersymmetry searches with ATLAS detector at LHC

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    In this paper, a brief overview of the principal strategies for Supersymmetry searches with ATLAS detector at LHC is presented. The aim is to evaluate the ATLAS discovery potential in inclusive channels with early data with particular attention to the more interesting techniques to estimate the principal SM backgrounds using real data

    Supersymmetry searches at LHC

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    In this paper, a brief overview of the principal strategies for Supersymmetry searches with both ATLAS and CMS detectors at LHC is presented. Particular attention will be devoted to the techniques to estimate the principal SM backgrounds using real data and to the discovery potential in the mSUGRA scenario

    Quark contact interactions at the LHC

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    Quark contact interactions are an important signal of new physics. We introduce a model in which the presence of a symmetry protects these new interactions from giving large corrections in flavor changing processes at low energies. This minimal model provides the basic set of operators which must be considered to contribute to the high-energy processes. To discuss their experimental signature in jet pairs produced in proton-proton colllisions, we simplify the number of possible operators down to two. We show (for a representative integrated luminosity of 200 pb^-1 at \surd s = 7 TeV) how the presence of two operators significantly modifies the bound on the characteristic energy scale of the contact interactions which is obtained by keeping a single operator.Comment: 8 pages, 2 figure

    A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery

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    The standard model of particle physics1-4 describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles5-9. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons-the carriers of the strong, electromagnetic and weak forces-are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (Ď„)) are well measured and indications of interactions with a second-generation particle (muons, ÎĽ) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model

    Comparison of established and emerging biodosimetry assays

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    Rapid biodosimetry tools are required to assist with triage in the case of a large-scale radiation incident. Here, we aimed to determine the dose-assessment accuracy of the well-established dicentric chromosome assay (DCA) and cytokinesis-block micronucleus assay (CBMN) in comparison to the emerging γ-H2AX foci and gene expression assays for triage mode biodosimetry and radiation injury assessment. Coded blood samples exposed to 10 X-ray doses (240 kVp, 1 Gy/min) of up to 6.4 Gy were sent to participants for dose estimation. Report times were documented for each laboratory and assay. The mean absolute difference (MAD) of estimated doses relative to the true doses was calculated. We also merged doses into binary dose categories of clinical relevance and examined accuracy, sensitivity and specificity of the assays. Dose estimates were reported by the first laboratories within 0.3-0.4 days of receipt of samples for the γ-H2AX and gene expression assays compared to 2.4 and 4 days for the DCA and CBMN assays, respectively. Irrespective of the assay we found a 2.5-4-fold variation of interlaboratory accuracy per assay and lowest MAD values for the DCA assay (0.16 Gy) followed by CBMN (0.34 Gy), gene expression (0.34 Gy) and γ-H2AX (0.45 Gy) foci assay. Binary categories of dose estimates could be discriminated with equal efficiency for all assays, but at doses ≥1.5 Gy a 10% decrease in efficiency was observed for the foci assay, which was still comparable to the CBMN assay. In conclusion, the DCA has been confirmed as the gold standard biodosimetry method, but in situations where speed and throughput are more important than ultimate accuracy, the emerging rapid molecular assays have the potential to become useful triage tools
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