@article{OPUS4-12890, title = {Measurement of the charge asymmetry in top quark pair production in pp collisions at √s=7 TeV using the ATLAS detector}, series = {The European Physical Journal C}, volume = {72}, journal = {The European Physical Journal C}, number = {2039}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2039-5}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128904}, year = {2012}, abstract = {A measurement of the top-antitop production charge asymmetry A C is presented using data corresponding to an integrated luminosity of 1.04 fb\(^{-1}\) of pp collisions at √s=7 TeV collected by the ATLAS detector at the LHC. Events are selected with a single lepton (electron or muon), missing transverse momentum and at least four jets of which at least one jet is identified as coming from a b-quark. A kinematic fit is used to reconstruct the t\(\overline t\) event topology. After background subtraction, a Bayesian unfolding procedure is performed to correct for acceptance and detector effects. The measured value of A\(_C\) is AC=-0.019±0.028 (stat.)±0.024 (syst.), consistent with the prediction from the MC@NLO Monte Carlo generator of A\(_C\) =0.006±0.002. Measurements of A\(_C\) in two ranges of invariant mass of the top-antitop pair are also shown.}, language = {en} } @article{OPUS4-12795, title = {A search for \(t\overline t\) resonances with the ATLAS detector in 2.05 fb\(^{-1}\) of proton-proton collisions at √s=7 TeV}, series = {European Physical Journal C}, volume = {72}, journal = {European Physical Journal C}, number = {2083}, organization = {ATLAS Collaboration}, doi = {10.1140/epjc/s10052-012-2083-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127959}, year = {2012}, abstract = {A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb\(^{-1}\), which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to \(t\overline t\) for narrow and wide resonances. For narrow Z′ bosons, the observed 95 \% Bayesian credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m Z′=500 GeV to m\(_{Z′}\)=1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z′ boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m\(_{Z′}\)<880 GeV (m\(_{gKK}\)<1130 GeV).}, language = {en} }