Top tagging: an analytical perspective

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In this paper we study aspects of top tagging from first principles of QCD. We find that the method known as the CMS top tagger becomes collinear unsafe at high pt and propose variants thereof which are IRC safe, and hence suitable for analytical studies, while giving a comparable performance to the CMS tagger. We also develop new techniques to identify three-pronged jet substructure, based on adaptations of the Y-splitter method and its combination with grooming. A novel feature of our studies, relative to previous calculations of two-pronged substructure, is our use of triple-collinear splitting functions combined with all-order resummation, which owes to the presence of two mass scales of the same order, mt and mW, in the signal jet. We carry out leading logarithmic resummed calculations for the various top-taggers, for both background and signal jets, and compare the results to those from parton showers. We also identify and comment on the main features driving tagger performance at high pt and discuss the role of non-perturbative effects.

Bibliographical metadata

Original languageEnglish
JournalJournal of High Energy Physics
Issue number9
Early online date28 Sep 2018
Publication statusPublished - Sep 2018

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