Jet Substructure Algorithms

Many physics models of electroweak symmetry breaking and solutions to the hierarchy problem predict the existence of heavy particles that often decay hadronically. If these new particles are boosted relative to their mass, the resulting decay products for hadronic decays can fall within a single jet. This summary explores the search and identification of these hadronically decaying boosted objects by examining the substructure of the jets that are postulated to originate from these boosted heavy particles. Examples of this include top quarks, W/Z bosons, Higgs bosons, and many others. Two algorithms have been proposed, one dedicated to reconstructing boosted top quarks and the other to identifying boosted W bosons. Both techniques are applied to data recorded by CMS in 2010 at 7 TeV and comparisons to various Monte Carlo generators and underlying event tunes are presented. A parametrization of the rate at which generic QCD jets are mistakenly identified by each algorithm is obtained from data. This parameterization allows background estimations for physics measurements and searches to be done using data-driven techniques.