Anders, J.K.; Beck, H.P.; Chatterjee, M.; Ereditato, A.; Franconi, L.; Halser, L.; Haug, S; Ilg, A.; Lehmann, N.; Mueller, R.; Weber, M.S. (2022). Measurement of the polarisation of single top quarks and antiquarks produced in the t-channel at √s = 13 TeV and bounds on the tWb dipole operator from the ATLAS experiment. Journal of High Energy Physics, 2022(11) Springer 10.1007/JHEP11(2022)040
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A simultaneous measurement of the three components of the top-quark and top-antiquark polarisation vectors in t-channel single-top-quark production is presented. This analysis is based on data from proton–proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 139 fb−1, collected with the ATLAS detector at the LHC. Selected events contain exactly one isolated electron or muon, large missing transverse momentum and exactly two jets, one being b-tagged. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from the background contributions. The top-quark and top-antiquark polarisation vectors are measured from the distributions of the direction cosines of the charged-lepton momentum in the top-quark rest frame. The three components of the polarisation vector for the selected top-quark event sample are Px′ = 0.01 ± 0.18, Py′ = −0.029 ± 0.027, Pz′ = 0.91 ± 0.10 and for the top-antiquark event sample they are Px′ = −0.02 ± 0.20, Py′ = −0.007 ± 0.051, Pz′ = 0.79 ± 0.16. Normalised differential cross-sections corrected to a fiducial region at the stable-particle level are presented as a function of the charged-lepton angles for top-quark and top-antiquark events inclusively and separately. These measurements are in agreement with Standard Model predictions. The angular differential cross-sections are used to derive bounds on the complex Wilson coefficient of the dimension-six OtW operator in the framework of an effective field theory. The obtained bounds are CtW ∈ [−0.9, 1.4] and CitW ∈ [−0.8, 0.2], both at 95% confidence level.
Item Type: |
Journal Article (Original Article) |
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Division/Institute: |
08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP) 10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC) |
UniBE Contributor: |
Anders, John Kenneth, Beck, Hans Peter, Chatterjee, Meghranjana, Ereditato, Antonio, Franconi, Laura, Halser, Lea, Haug, Sigve, Ilg, Armin, Lehmann, Niklaus, Müller, Roman, Weber, Michele |
Subjects: |
500 Science > 530 Physics |
ISSN: |
1029-8479 |
Publisher: |
Springer |
Language: |
English |
Submitter: |
BORIS Import LHEP |
Date Deposited: |
06 Apr 2023 08:30 |
Last Modified: |
13 Apr 2023 14:52 |
Publisher DOI: |
10.1007/JHEP11(2022)040 |
Additional Information: |
Kollaboration - Es sind nur die Berner Autor*innen namentlich erwaehnt; the ATLAS collaboration |
BORIS DOI: |
10.48350/181417 |
URI: |
https://boris.unibe.ch/id/eprint/181417 |
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