Search for new phenomena in tt̅ events with large missing transverse momentum in proton-proton collisions at √s=7 TeV with the ATLAS detector

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.