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T: Fachverband Teilchenphysik
T 79: Top quark production III
T 79.9: Vortrag
Donnerstag, 18. März 2021, 18:00–18:15, Td
Studies on the reconstruction of multiple top quarks in the tttt production in same-sign dilepton final states using Boosted Decision Trees with the ATLAS detector — Vakhtang Ananiashvili1, Peter Johannes Falke1, •Ö. Oğul Öncel1, Niklas Werner Schwan1, and Markus Cristinziani2 — 1Physikalisches Institut, Universität Bonn — 2Center for Particle Physics Siegen, Experimentelle Teilchenphysik, Universität Siegen
Recently, ATLAS has established the evidence for the tttt process in the same-sign dilepton and multilepton channels, using data collected at the LHC during 2015–2018 with 139.4 fb−1 integrated luminosity and at a centre-of-mass energy of 13 TeV.
The analysis is impacted particularly from large ttZ, ttH, and ttW backgrounds, as well as small but persistent ttt background. This talk presents studies made on the reconstruction of multiple top-quarks in the same-sign dilepton final states of the tttt process. The tttt process presents significant challenges for top-quark reconstruction in both, hadronic and leptonic decay modes due to the large number of jets, inflating the possible number of combinations, as well as multiple neutrinos in the event that cannot be reconstructed by the detector.
Boosted Decision Trees are employed to reconstruct top-quarks based on an object-level training, in which all possible combinations in an event are evaluated and assigned a score. The performance of the reconstruction is investigated by comparison to Monte-Carlo truth information, and its impact on the analysis sensitivity is evaluated by using this additional information in the statistical analysis.