UNSPECIFIED (2012) Search for new phenomena in tt¯ events with large missing transverse momentum in proton-proton collisions at s√=7 TeV with the ATLAS detector. Physical review letters, 108 (4): 041805. ISSN 1079-7114
PhysRevLett.108.041805.pdf - Published Version
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Abstract
A search for new phenomena in tt¯ events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04 fb−1 of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb for a top-partner mass of 420 GeV and a neutral particle mass less than 10 GeV. In a model of exotic fourth generation quarks, top-partner masses are excluded up to 420 GeV and neutral particle masses up to 140 GeV.