1,355 research outputs found

    Measurement of the cross-section for b-jets produced in association with a Z boson at sqrt(s) = 7 TeV with the ATLAS detector

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    In this thesis, 4.7 fb^(-1) of data taken in 2011 by the ATLAS Experiment of proton-proton collisions at sqrt(s) = 7 TeV delivered by the Large Hadron Collider at CERN is used to measure the integrated and differential cross sections for the production of electroweak Z bosons in associaton with b quark jets. Z bosons are identified by reconstructing the electron and muon decay modes, and the fraction of b quark jets in the Z sample is estimated by fitting the neural network output of a specialised heavy flavour tagging algorithm in data with light + charm and bottom flavour templates derived from Monte Carlo simulation. The integrated Z + b jet cross section is measured to be 5.04 +- 0.17 stat +- 0.83 syst pb. The ratio of the integrated Z + b jet cross section to the inclusive Z production cross section is measured to be (5.26 +- 0.18 stat +- 0.89 syst) 10^(-3). The integrated Z +b jet cross section is also measured differentially in bins of b jet transverse energy, b jet rapidity, and Z boson transverse momentum. These measurements are compared to predictions from leading order Monte Carlo generators and next-to-leading-order QCD calculations. Also contained within this thesis are contributions to the commissioning of the ATLAS detector with early data, and studies produced for the calibration of software algorithms used in the tagging of heavy flavour jets. The resolution of the ATLAS inner detector is measured using data recorded by ATLAS in 2009. Systematic effects resulting in discrepancies between the efficiency to identify heavy flavour jets in data and simulation are measured using 2010 ATLAS data

    Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

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    The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +cÂŻÂŻ)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−sÂŻÂŻÂŻ quark asymmetry

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an