Hollow cone sieve for top
  A method of top tagging is introduced. Using the anti-kt algorithm to define jets, events with nj = 2 fat jets of cone size R = 1.5 are decomposed into R = 0.6 sub-jets and retained if nj (R= 0.6) >= 4 . One pair of sub-jets reconstructs the W-mass and another jet is tagged as a b-jet, as necessary for hadronic or semileptonic events of tt origin. This 'hollow cone' method distinguishes the tt events from the light parton QCD dijet events. 
Vernon Barger, Peisi Huang
hep-ph hep-ex