A search for ttbar resonance in the lepton plus jets channel with ATLAS using 14fb-1 of proton proton collisions at $\sqrt{s}$ = 8 TeV

The search for ttbar resonances that could be produced at the CERN Large Hadron Collider allow the investigation of a wide range of physics beyond the Standard Model. In such a scheme, the top quark is often produced with a transverse momentum that is large as compared to its mass and the decay of such highly boosted top often leads to a topology that differs in several respects from that encountered when the top quarks are produced approximately at rest. A search for new particles that decay into top quark pairs is performed with the ATLAS experiment at the LHC using an integrated luminosity of 14~fb$^{-1}$ of proton-proton collisions data collected at center-of-mass energy $sqrt{s}$ = 8~TeV. No evidence for a $tar{t}$ resonance is found and 95% CL limits on the production rate are determined for massive states in two benchmark models. Hence, narrow leptophobic topcolor Z' boson with a mass below 1.8~TeV is excluded and a Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.0 TeV.