A search for t(t) over-bar resonances in lepton plus jets events with highly boosted top quarks collected in pp collisions at √s = 7 TeV with the ATLAS detector

Abstract

A search for resonant production of high-mass top-quark pairs is performed on 2.05 fb−1 of proton-proton collisions at √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(t) over-bar invariant mass spectrum is found to be compatible with the Standard Model prediction and 95% credibility level upper limits are derived on the t(t) over-bar 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.