ATLAS Boosted Object Tagging

Tagging boosted top quarks with the ATLAS detector at sqrt(s)=8 TeV and sqrt(s)=13 TeV Different methods to identify high-pT top quarks based on substructure analyses are studied using pp collision data and MC simulations at sqrt(s)=8 TeV. An enriched ttbar sample is used to measure the top selection efficiency in data for substructure-based taggers as well as the HEPTopTagger and Shower Deconstruction algorithms. An enriched QCD sample is used to measure the misidentification rate for these algorithms. In addition, MC simulations at sqrt(s)=13 TeV with 2015 data-taking conditions are used to determine substructure-based taggers and their systematic uncertainties for use by early data analyses. Data/MC comparisons of these variables with early data are also shown. Tagging boosted Higgs bosons with the ATLAS detector at sqrt(s)=8 TeV and sqrt(s)=13 TeV The identification of boosted Higgs bosons decaying to a pair of b-quarks is studied using pp collision data at sqrt(s)=8 TeV and MC simulations at sqrt(s)=8 TeV and sqrt(s)=13 TeV. Independent tagging variables optimal for rejecting different types of backgrounds are found and they are studied in g->bb enriched and ttbar enriched samples in data. These same variables are studied in early 2015 data at sqrt(s)=13 TeV and systematic uncertainties on the tagging efficiencies are determined for use by early 2015 physics analyses.