Based on Phys.Rev.Lett. 101 (2008) 142001 (arXiv:0806.0848) by David E. Kaplan, Keith Rehermann, Matthew D. Schwartz and Brock Tweedie


This paper described the Hopkins top-tagging, which is currently being used by CMS to look for new physics top-antitop resonances. The idea is that when a top is boosted it decays to 3 collimated jets, which are not found as separate jets with a classic jet algorithm. Instead, you have to take a larger jet and then recluster using jet substructure. The algorithm is

  1. Cluster with a fat jet size, R=1.2
  2. Look for the 3 or 4 hardest subjets
  3. Have 2 subjets reconstruct the W mass
  4. Have the 3 or 4 reconstruct the top mass

Here are some relevant distributions

First cut on the splitting scale

Then cut on the top mass Then cut on W mass

Top-tagging helps find new physics

Before and After top-tagging

 

Red is the background and Blue the signal. Dashed is before top-tagging, Solid afterward

CMS has measured tops using this method. Here is a tog-tagged event