Measurement of the polarisation of single top quarks and antiquarks produced in the t-channel at s $$ \sqrt{s} $$ = 13 TeV and bounds on the tWb dipole operator from the ATLAS experiment
Springer, 2022
Online
academicJournal
- 62
Zugriff:
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 P x ′ $$ {P}_{x^{\prime }} $$ = 0.01 ± 0.18, P y ′ $$ {P}_{y^{\prime }} $$ = −0.029 ± 0.027, P z ′ $$ {P}_{z^{\prime }} $$ = 0.91 ± 0.10 and for the top-antiquark event sample they are P x ′ $$ {P}_{x^{\prime }} $$ = −0.02 ± 0.20, P y ′ $$ {P}_{y^{\prime }} $$ = −0.007 ± 0.051, P z ′ $$ {P}_{z^{\prime }} $$ = 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 O $$ \mathcal{O} $$ tW operator in the framework of an effective field theory. The obtained bounds are C tW ∈ [−0.9, 1.4] and C itW ∈ [−0.8, 0.2], both at 95% confidence level.
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Measurement of the polarisation of single top quarks and antiquarks produced in the t-channel at s $$ \sqrt{s} $$ = 13 TeV and bounds on the tWb dipole operator from the ATLAS experiment
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Autor/in / Beteiligte Person: | Aad, G. ; Abbott, B. ; Abbott, D. ; Abed Abud, A. ; Abeling, K. ; Abhayasinghe, D. ; Abidi, S. ; Abramowicz, H. ; Abreu, H. ; Abulaiti, Y. ; Abusleme Hoffman, A. ; Acharya, B. ; Achkar, B. ; Adam, L. ; Adam Bourdarios, C. ; Adamczyk, L. ; Adamek, L. ; Addepalli, S. ; Adelman, J. ; Adiguzel, A. ; Adorni, S. ; Adye, T. ; Affolder, A. ; Afik, Y. ; Agapopoulou, C. ; Agaras, M. |
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Veröffentlichung: | Springer, 2022 |
Medientyp: | academicJournal |
Umfang: | 62 |
DOI: | 10.1007/JHEP11(2022)040 |
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