Top tagging: A method for identifying boosted hadronically decaying top quarks

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) similar or equal to 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 (t) over bar resonances by a factor of similar to 10000, thereby allowing resonance searches in t (t) over bar to be extended into the all-hadronic channel. In addition, top tagging can be used in t (t) over bar events when one of the top quarks decays semileptonically, in events with missing energy, and in studies of b-tagging efficiency at high p(T).