  Some Beyond the Standard Model theories predict new particles that decay
predominantly into top-antitop quark pairs. A search for top-antitop quark
resonances that decay into the lepton plus jets final state is carried out with
the ATLAS experiment at the LHC using 14 fb$^{-1}$ of $\sqrt{s}$ = 8 TeV
proton-proton collisions. The search considers both cases where all of the
final state jets are isolated and where some or all of the top quark decay
products are merged into a single jet. Mass exclusion limits at a 95%
credibility level are set for two benchmark models, one predicting leptophobic
topcolor Z' bosons and the other predicting Randall-Sundrum Kaluza-Klein
gluons.
