A search for $ t\overline t $ resonances in lepton+jets events with highly boosted top quarks collected in pp collisions at $ \sqrt {s} = 7 $ TeV with the ATLAS detector

Abstract

AbstractA search for resonant production of high-mass top-quark pairs is performed on 2.05 fb−1of proton-proton collisions at$ \sqrt {s} = 7 $TeV collected in 2011 with the ATLAS experiment at the Large Hadron Collider. This analysis of the lepton+jets final state is specifically designed for the particular topology that arises from the decay of highly boosted top quarks. The observed$ t\overline t $invariant mass spectrum is found to be compatible with the Standard Model prediction and 95% credibility level upper limits are derived on the$ t\overline t $production rate through new massive states. An upper limit of 0.7 pb is set on the production cross section times branching fraction of a narrow 1 TeV resonance. A Kaluza-Klein gluon with a mass smaller than 1.5 TeV is excluded.