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Search for new phenomena with top-quark pairs and large missing transverse momentum using 140 fb−1 of pp collision data at s = 13 TeV with the ATLAS detector

Aad, G. ; Åkesson, T.P.A. LU orcid ; Astrand, K.S.V. LU ; Doglioni, C. LU ; Ekman, P.A. LU orcid ; Hedberg, V. LU ; Herde, H. LU orcid ; Konya, B. LU ; Lytken, E. LU orcid and Poettgen, R. LU orcid , et al. (2024) In Journal of High Energy Physics 2024(3).
Abstract
A search is conducted for new phenomena in events with a top quark pair and large missing transverse momentum, where the top quark pair is reconstructed in final states with one isolated electron or muon and multiple jets. The search is performed using the Large Hadron Collider proton-proton collision data sample at a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector that corresponds to an integrated luminosity of 140 fb−1. An analysis based on neural network classifiers is optimised to search for directly produced pairs of supersymmetric partners of the top quark (stop), and to search for spin-0 mediators, produced in association with a pair of top quarks, that decay into dark-matter particles. In the stop search, the... (More)
A search is conducted for new phenomena in events with a top quark pair and large missing transverse momentum, where the top quark pair is reconstructed in final states with one isolated electron or muon and multiple jets. The search is performed using the Large Hadron Collider proton-proton collision data sample at a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector that corresponds to an integrated luminosity of 140 fb−1. An analysis based on neural network classifiers is optimised to search for directly produced pairs of supersymmetric partners of the top quark (stop), and to search for spin-0 mediators, produced in association with a pair of top quarks, that decay into dark-matter particles. In the stop search, the analysis is designed to target models in which the mass difference between the stop and the neutralino from the stop decay is close to the top quark mass. This new search is combined with previously published searches in final states with different lepton multiplicities. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set. Models with neutralinos with masses up to 570 GeV are excluded, while for small neutralino masses models are excluded for stop masses up to 1230 GeV. Scalar (pseudoscalar) dark matter mediator masses as large as 350 (370) GeV are excluded when the coupling strengths of the mediator to Standard Model and dark-matter particles are both set to one. At lower mediator masses, models with production cross-sections as small as 0.15 (0.16) times the nominal predictions are excluded. Results of this search are also used to set constraints on effective four-fermion contact interactions between top quarks and neutrinos. © The Author(s) 2024. (Less)
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type
Contribution to journal
publication status
published
subject
keywords
Hadron-Hadron Scattering
in
Journal of High Energy Physics
volume
2024
issue
3
article number
139
publisher
Springer
external identifiers
  • scopus:85193029940
ISSN
1029-8479
DOI
10.1007/JHEP03(2024)139
language
English
LU publication?
yes
id
27beeacf-988f-4d62-a6fd-d602e80a5689
date added to LUP
2025-12-11 16:21:26
date last changed
2025-12-11 16:22:28
@article{27beeacf-988f-4d62-a6fd-d602e80a5689,
  abstract     = {{A search is conducted for new phenomena in events with a top quark pair and large missing transverse momentum, where the top quark pair is reconstructed in final states with one isolated electron or muon and multiple jets. The search is performed using the Large Hadron Collider proton-proton collision data sample at a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector that corresponds to an integrated luminosity of 140 fb−1. An analysis based on neural network classifiers is optimised to search for directly produced pairs of supersymmetric partners of the top quark (stop), and to search for spin-0 mediators, produced in association with a pair of top quarks, that decay into dark-matter particles. In the stop search, the analysis is designed to target models in which the mass difference between the stop and the neutralino from the stop decay is close to the top quark mass. This new search is combined with previously published searches in final states with different lepton multiplicities. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set. Models with neutralinos with masses up to 570 GeV are excluded, while for small neutralino masses models are excluded for stop masses up to 1230 GeV. Scalar (pseudoscalar) dark matter mediator masses as large as 350 (370) GeV are excluded when the coupling strengths of the mediator to Standard Model and dark-matter particles are both set to one. At lower mediator masses, models with production cross-sections as small as 0.15 (0.16) times the nominal predictions are excluded. Results of this search are also used to set constraints on effective four-fermion contact interactions between top quarks and neutrinos. © The Author(s) 2024.}},
  author       = {{Aad, G. and Åkesson, T.P.A. and Astrand, K.S.V. and Doglioni, C. and Ekman, P.A. and Hedberg, V. and Herde, H. and Konya, B. and Lytken, E. and Poettgen, R. and Simpson, N.D. and Smirnova, O. and Wallin, E.J. and Zwalinski, L.}},
  issn         = {{1029-8479}},
  keywords     = {{Hadron-Hadron Scattering}},
  language     = {{eng}},
  number       = {{3}},
  publisher    = {{Springer}},
  series       = {{Journal of High Energy Physics}},
  title        = {{Search for new phenomena with top-quark pairs and large missing transverse momentum using 140 fb−1 of pp collision data at s = 13 TeV with the ATLAS detector}},
  url          = {{http://dx.doi.org/10.1007/JHEP03(2024)139}},
  doi          = {{10.1007/JHEP03(2024)139}},
  volume       = {{2024}},
  year         = {{2024}},
}