Top-Tagging: A Method for Identifying Boosted Hadronic Tops

Abstract

A method is introduced for distinguishing top jets (boosted, hadronically decaying top quarks) from light quark and gluon jets using jet substructure. The procedure involves parsing the jet cluster to resolve its subjets, and then imposing kinematic constraints. With this method, light quark or gluon jets with (p_T \simeq) 1 TeV can be rejected with an efficiency of around 99% while retaining up to 40% of top jets. This reduces the dijet background to heavy (t\bar{t}) resonances by a factor of ~10,000, thereby allowing resonance searches in (t\bar{t}) to be extended into the all-hadronic channel. In addition, top-tagging can be used in (t\bar{t}) events when one of the tops decays semi-leptonically, in events with missing energy, and in studies of b-tagging efficiency at high (p_T).