Parts | Days | Selection | Search | Updates | Downloads | Help
T: Fachverband Teilchenphysik
T 63: Top-Quarks: Paarproduktion
T 63.5: Talk
Tuesday, March 25, 2014, 17:45–18:00, P104
Variable-R Jets for tt Resonance Searches with the ATLAS detector — •Katharina Behr and Çiğdem Işsever — Sub-department of Particle Physics, University of Oxford, Denys-Wilkinson Building, Keble Road, Oxford OX1 3RH, United Kingdom
Heavy exotic resonances that decay to tt pairs are predicted by a range of extensions to the Standard Model such as Randall-Sundrum warped extra-dimension or top-colour assisted technicolour models. Current searches based on Run-I LHC data set lower exclusion limits on the resonance masses for benchmark models in the TeV range. The top quarks from these resonance decays typically have large transverse momenta pT,top (“boosted” top quarks) and the separation between their decay products decreases inversely with pT,top which makes the decay products likely to overlap and thereby difficult to resolve. Instead of reconstructing the individual decay products current (hadronic) top taggers therefore treat boosted top quarks as a single large-R jet with fixed R-parameter.
We show that these fixed-R jets over-estimate the real top jet size which decreases like pT,top−1 and that jets for which R scales like pT,top−1 (Variable-R jets) provide a more natural description of boosted hadronic top quarks while - due to their smaller areas - suffering significantly less from soft contaminations introduced by pile-up and the Underlying Event than large fixed-R jets. In this talk, I will discuss both the choice of jet parameters and the performance of Variable-R jets in searches for new physics in final states with boosted top quarks.