2 research outputs found

    Measurements of the charge asymmetry in top-quark pair production in the dilepton final state at s √ =8  TeV with the ATLAS detector

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    Measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel, characterized by two high-pT leptons (electrons or muons), are presented using data corresponding to an integrated luminosity of 20.3  fb−1 from pp collisions at a center-of-mass energy s√=8  TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the ttÂŻ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: AℓℓC based on the selected leptons and AttÂŻC based on the reconstructed ttÂŻ final state. The inclusive asymmetries are measured in the full phase space to be AℓℓC=0.008±0.006 and AttÂŻC=0.021±0.016, which are in agreement with the Standard Model predictions of AℓℓC=0.0064±0.0003 and AttÂŻC=0.0111±0.0004

    A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector

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    A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb−1 − 1 of √ s = 13 TeV pp collision data recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the background prediction is observed. Results are interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, ̃ t ~ , which decays promptly into two quarks through R-parity-violating couplings. Top squarks with masses in the range 100 GeV<̃<410 100 GeV < m t ~ < 410 GeV GeV are excluded at 95% confidence level. If the decay is into a b-quark and a light quark, a dedicated selection requiring two b-tags is used to exclude masses in the ranges 100 GeV<̃<470 100 GeV < m t ~ < 470 GeV GeV and 480 GeV<̃<610 480 GeV < m t ~ < 610 GeV GeV . Additional limits are set on the pair-production of massive colour-octet resonances
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