Prospects for top anti-top resonance searches using early ATLAS data.

Searches for signatures of new physics in top anti-top events at the LHC require efficient reconstruction of top quarks with a broad range of transverse momenta. Three new reconstruction schemes are developed to deal with the large variety of top decay topologies. Their performance on the lepton + jets final state is evaluated using a detailed simulation of signal and background processes. Compared to previous ATLAS studies, a much improved reconstruction efficiency is found over a large top anti-top invariant mass range. As a consequence, the sensitivity to top anti-top resonances in the TeV regime is enhanced considerably. Even in the earliest phase of the experiment, with an integrated luminosity of less than 1/fb at a reduced center-of-mass energy of 7 TeV, ATLAS is expected to significantly extend the mass reach of existing searches.