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

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dc.contributor.authorAad, G.
dc.contributor.authorAbbott, B.
dc.contributor.authorAbbott, D.C.
dc.contributor.authorAbed Abud, A.
dc.contributor.authorAbeling, K.
dc.contributor.authorAbhayasinghe, D.K.
dc.contributor.authorAbidi, S.H.
dc.contributor.authorAbramowicz, H.
dc.contributor.authorAbreu, H.
dc.contributor.authorAbulaiti, Y.
dc.contributor.authorAbusleme Hoffman, A.C.
dc.contributor.authorAcharya, B.S.
dc.contributor.authorAchkar, B.
dc.contributor.authorAdam, L.
dc.contributor.authorAdam Bourdarios, C.
dc.contributor.authorAdamczyk, L.
dc.contributor.authorAdamek, L.
dc.contributor.authorAddepalli, S.V.
dc.contributor.authorAdelman, J.
dc.contributor.authorAdiguzel, A.
dc.contributor.authoret al.
dc.date.issued2022
dc.descriptionPublished: November 9, 2022
dc.description.abstractA 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.
dc.description.statementofresponsibilityG. Aad ... P. Jackson ... A.X.Y. Kong ... H. Potti ... T.A. Ruggeri .. A.S. Sharma ... M.J. White ... et al. (The ATLAS collaboration)
dc.identifier.citationJournal of High Energy Physics (JHEP), 2022; 2022(11):40-1-40-62
dc.identifier.doi10.1007/jhep11(2022)040
dc.identifier.issn1029-8479
dc.identifier.issn1029-8479
dc.identifier.orcidJackson, P. [0000-0002-0847-402X]
dc.identifier.orcidMcDougall, A.E. [0000-0001-7713-2800]
dc.identifier.orcidPotti, H. [0000-0002-0800-9902]
dc.identifier.orcidWhite, M.J. [0000-0001-5474-4580]
dc.identifier.urihttps://hdl.handle.net/2440/137072
dc.language.isoen
dc.publisherSpringer
dc.rightsOpen Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. SCOAP3 supports the goals of the International Year of Basic Sciences for Sustainable Development.
dc.source.urihttps://doi.org/10.1007/jhep11(2022)040
dc.subjectHadron-Hadron Scattering; Top Physics
dc.titleMeasurement 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
dc.title.alternativeMeasurement of the polarisation of single top quarks and antiquarks produced in the t-channel at s root = 13 TeV and bounds on the tWb dipole operator from the ATLAS experiment
dc.typeJournal article
pubs.publication-statusPublished

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