Wuppertal 2015 – scientific programme
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T: Fachverband Teilchenphysik
T 46: Top: Boosted b-tagging, single top
T 46.2: Talk
Tuesday, March 10, 2015, 17:00–17:15, L.09.31 (HS 11)
High-pT B-tagging and Top-Tagging with Variable-R Jets in ATLAS — •Katharina Behr — Sub-department of Particle Physics, University of Oxford, Denys-Wilkinson Building, Keble Road, Oxford OX1 3RH, United Kingdom
Variable-R jets, whose effective size is inversely proportional to their transverse momentum, are a versatile tool for object reconstruction across the large transverse momentum regime accessible during Run 2 of the LHC. I will discuss the performance of Variable-R jets in two different contexts:
1) Boosted top-tagging. The separation between the decay products of highly energetic top quarks decreases with pTtop causing them to overlap and merge into a single jet. Taggers relying on large fixed-R jets overestimate the real size of the top jet in the highly boosted regime and are more susceptible to the effects of pile-up. Variable-R jets are studied as the basis for more natural taggers which may not even require grooming.
2) B-tagging. The b-tagging performance in boosted topologies suffers in the presence of close-by jets. This limits the sensitivity of many searches such as those in boosted hh→ 4b final states. New b-taggers relying on track jets with smaller sizes than the traditional R=0.4 to better isolate the b-hadron decay show significant improvements in highly boosted scenarios but perform worse at low transverse momenta where they fail to capture the full b-jet. Variable-R track jets provide a unified approach to b-tagging in both pT regimes.