3,003 research outputs found

    Feasibility of Beauty Baryon Polarization Measurement in Lambda0 J/psi Decay Channel by Atlas-LHC

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    The possibility of beauty baryon polarization measurement by cascade decay angular distribution analysis in the channel Lambda0 J/psi --> p pi- l+ l- is demonstrated. The error analysis shows that in the proposed LHC experiment ATLAS at the luminosity 104pb110^{4} pb^{-1} the polarization can be measured with the statistical precision better than δ=0.010\delta=0.010 for Lambda_b0 and δ=0.17\delta=0.17 for Xi_b0.Comment: 12 pages (LaTeX + AMS-LaTeX) and 3 figures in postscript (uuencoded, compressed tar file included at the end of the paper), PRA-HEP-94/

    Backgrounds for rare muonic B-meson decays in ATLAS

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    The work gives an overview of expected exclusive backgrounds for rare muonic B-meson decays in ATLAS. Based on theoretical calculations and a modelling in Generators, followed by phase space cuts according to fiducial detector volume and trigger acceptance, the authors classify all possible backgrounds according to their importance and select those requiring full detector simulation. The most importat background comes from Bd0πμ+νμB_d^0 \to \pi^- \mu^+ \nu_{\mu}, when a charged pion decays in a detector volume producing a secondary muon. Similar mechanism would lead to a background comming from B-mesons decaying to two charged hadrons. Another important background is from B+μ+μl+νB^+ \to \mu^+\mu^-l^+ \nu.This note gives an overview of expected exclusive backgrounds for rare muonic B–meson decays at ATLAS from the theoretical point of view. The goal of this work is to show which of backgrounds are most important for further full detector simulation. It is shown that the most important noncombinatorial background comes from Bd0πμ+νμB_d^0 \to \pi^- \mu^+ \nu_{\mu} fake rate. Another important BG sources are B+μ+μ+ν,Bc+J/ψ(μ+μ)νB^+ \to \mu^+\mu^-\ell^+ \nu_{\ell}, B_c^+ \to J/\psi (\mu^+ \mu^-) \ell \nu_{\ell} and two-body hadronic B–meson decays

    Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

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    The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

    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