Top tagging in Run 1 and early Run 2 commissioning with the ATLAS detector

This note presents studies of the performance of several jet substructure techniques to identify high transverse momentum top quarks. The top tagging efficiency and misidentification rate are measured using a top quark pair and a multijet event sample collected with the ATLAS experiment in 20.3 $fb^{-1}$ of 8 TeV proton-proton collisions at the Large Hadron Collider in 2012. Predictions from Monte Carlo simulations are found to provide an accurate description of the performance. The techniques are compared in terms of signal efficiency and background rejection using simulations, covering a larger range in jet transverse momenta than accessible in the dataset. Additionally a novel technique is developed that is optimised to reconstruct top quarks in events with many jets.