Brock Tweedie (Johns Hopkins)
Tagging Hadronic Tops at High Pt
September 09, 2008

New heavy particles that decay to top quarks are nearly ubiquitous in
models that address the stability of the electroweak scale.  If the masses
of these particles are above about 1 TeV, the tops that they produce will
be highly boosted and in turn decay into highly collimated jets of
particles.  This complicates the standard top identification techniques
using multiple isolated jets and leptons, and the high track density may
severely degrade the reliability of b-tagging.  I will discuss a new
method for identifying boosted top quarks, which recovers the full 3-body
kinematics by first clustering all decay products into one jet, and then
reversing the clustering steps to pick out the hard substructures.  For
fully hadronic top decays, this method achieves a tag rate of 40% for tops
at pt ~ 1 TeV, while rejecting 98~99% of quark and gluon jets, without
requiring a b tag.