A search for ttbar resonances in the lepton plus jets final state using 4.66 fb^-1 of pp collisions at sqrt(s) = 7 TeV

A search for new particles that decay into ttbar pairs is performed with the ATLAS experiment at the LHC using 4.66 fb^-1 of data collected at 7 TeV. The ttbar system is reconstructed using the lepton plus jets decay channel, both with standard jets and by exploiting jet substructure. No evidence for a ttbar resonance is observed. For a narrow Z' boson, the 95% credibility level cross section times branching ratio upper limits range from 3.2 pb at a resonance mass of 0.7 TeV to 0.05 for a mass of 2 TeV. Leptophobic topcolor Z' resonances are excluded for masses below 1.7 TeV and Randall-Sundrum Kaluza-Klein gluon excitations are excluded for masses below 1.9 TeV at a 95% credibility level.