959 resultados para Johnston, Sarah Iles
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The inclusive production cross sections for forward jets, as well for jets in dijet events with at least one jet emitted at central and the other at forward pseudorapidities, are measured in the range of transverse momenta p(T) = 35-150 GeV/c in proton-proton collisions at root s = 7 TeV by the CMS experiment at the LHC. Forward jets are measured within pseudorapidities 3.2<|eta|<4.7, and central jets within the |eta|<2.8 range. The double differential cross sections with respect to pt and eta are compared to predictions from three approaches in perturbative quantum chromodynamics: (i) next-to-leading-order calculations obtained with and without matching to parton-shower Monte Carlo simulations, (ii) PYTHIA and HERWIG parton-shower event generators with different tunes of parameters, and (iii) CASCADE and HEJ models, including different non-collinear corrections to standard single-parton radiation. The single-jet inclusive forward jet spectrum is well described by all models, but not all predictions are consistent with the spectra observed for the forward-central dijet events.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Search for dark matter and large extra dimensions in monojet events in pp collisions at root s=7 TeV
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Relata-se a ocorrência de Contracaecum pelagicum Johnston & Mawson 1942 (Nematoda, Anisakidae) em um novo hospedeiro, Sula leucogaster Boddaert 1783 (Pelecaniformes, Sulidae), espécie conhecida como atobá. Três machos e três fêmeas dessa espécie de nematódeo foram coletados no regurgito da ave. Pela análise morfológica conclui-se que C. pelagicum era a espécie envolvida no parasitismo. Este é o primeiro relato sobre a ocorrência de nematódeos do gênero Contracaecum em S. leucogaster.
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The Drell-Yan differential cross section is measured in pp collisions at √ s = 7TeV, from a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb-1. The cross section measurement, normalized to the measured cross section in the Z region, is reported for both the dimuon and dielectron channels in the dilepton invariant mass range 15{600 GeV. The normalized cross section values are quoted both in the full phase space and within the detector acceptance. The effect of final state radiation is also identified. The results are found to agree with theoretical predictions. Copyright CERN.
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A measurement of the J/ ψ and ψ (2S) production cross sections in pp collisions at √s = 7TeV with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of 37 pb -1. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges and integrated in the kinematical regions considered in this study. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B → ψ (2S)X decay is extracted from the ratio of the non-prompt cross sections to be: B(B → ψ (2S)X) = (3:08 ± 0:12 (stat.+syst.) ± 0:13 (theor.) ± 0:42 (BPDG)) × 10 -3: B(B → ψ(2S)X) = (3.08 ± 0.12 (stat.+syst.) ± 0.13 (theor.) ± 0.42 (B PDG)) × 10 -3.
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Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark t → H +b and which, in turn, decays into τ +ν t. The analysed data correspond to an integrated luminosity of about 2 fb -1 recorded in protonproton collisions at √s = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs tt̄ → H ±W ∓bb̄ and tt̄ → H ±H ∓bb̄. Various final states have been studied separately, all requiring presence of a τ lepton from H + decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t → H +b) in the range of 2-4% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(H + → τ +ν τ) = 1.