Accuracy versus precision in boosted top tagging with the ATLAS detector
Authors
Aad, G.; Aakvaag, E.; Abbott, B.; Abdelhameed, S.; Ali, B.; Augsten, K.; Bergmann, B.; Day-Hall, H.; 438165; Hubáček, Z.; Mondal, S.; Myška, M.; Novotný, L.; Petousis, V.; Pospíšil, S.; Smolek, K.; Sopczak, A.; Vacek, V.; Vokáč, P.; Zaplatílek, O.
Year
2024
Published
Journal of Instrumentation. 2024, 19(8), ISSN 1748-0221.
Type
Article
Departments
Annotation
The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.
Search for pair-produced vectorlike quarks coupling to light quarks in the lepton plus jets final state using 13 TeV pp collisions with the ATLAS detector
Authors
Aad, G.; Aakvaag, E.; Abbott, B.; Abdelhameed, S.; Ali, B.; Augsten, K.; Bergmann, B.; Day-Hall, H.; 438165; Hubáček, Z.; Mondal, S.; Myška, M.; Novotný, L.; Petousis, V.; Pospíšil, S.; Smolek, K.; Sopczak, A.; Vacek, V.; Vokáč, P.; Zaplatílek, O.
Year
2024
Published
Physical Review D. 2024, 110(5), ISSN 2470-0029.
Type
Article
Departments
Annotation
A search is presented for the pair production of heavy vectorlike quarks (VLQs) that each decay into a W boson and a light quark. This study focuses on events where one W boson decays into leptons and the other into hadrons. The search analyzed 140 fb(-1) of pp collision data with root s = 13 TeV, recorded by the ATLAS detector from 2015 to 2018 during run 2 of the Large Hadron Collider. The final state is characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, multiple small-radius jets, and a single large-radius jet identified as originating from the hadronic decay of a boosted W boson. With higher center-of-mass energy and integrated luminosity than in the run 1 search, and improved analysis tools, this analysis excludes VLQs (Q) with masses below 1530 GeVat 95% confidence level for the branching ratio B(Q -> Wq) = 1, an improvement of 840 GeV on the previous ATLAS limit.