| 171. |
- Aad, G, et al.
(författare)
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Search for trilepton resonances from chargino and neutralino pair production in s =13 TeV pp collisions with the ATLAS detector
- 2021
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Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 103:11
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Tidskriftsartikel (refereegranskat)abstract
- A search is performed for the electroweak pair production of charginos and associated production of a chargino and neutralino, each of which decays through an R-parity-violating coupling into a lepton and a W, Z, or Higgs boson. The trilepton invariant-mass spectrum is constructed from events with three or more leptons, targeting chargino decays that include an electron or muon and a leptonically decaying Z boson. The analyzed dataset corresponds to an integrated luminosity of 139 fb-1 of proton-proton collision data produced by the Large Hadron Collider at a center-of-mass energy of s=13 TeV and collected by the ATLAS experiment between 2015 and 2018. The data are found to be consistent with predictions from the Standard Model. The results are interpreted as limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model. Limits are also set on the production of charginos and neutralinos for a minimal supersymmetric Standard Model with an approximate B-L symmetry. Charginos and neutralinos with masses between 100 and 1100 GeV are excluded depending on the assumed decay branching fractions into a lepton (electron, muon, or τ lepton) plus a boson (W, Z, or Higgs). © 2021 CERN.
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| 172. |
- Aad, G, et al.
(författare)
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Search for tt¯ resonances in fully hadronic final states in pp collisions at √s = 13 TeV with the ATLAS detector
- 2020
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Ingår i: Journal of High Energy Physics. - : Springer Nature. - 1029-8479 .- 1126-6708. ; 2020:10
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a search for new heavy particles decaying into a pair of top quarks using 139 fb−1 of proton-proton collision data recorded at a centre-of-mass energy of s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The search is performed using events consistent with pair production of high-transverse-momentum top quarks and their subsequent decays into the fully hadronic final states. The analysis is optimized for resonances decaying into a tt¯ pair with mass above 1.4 TeV, exploiting a dedicated multivariate technique with jet substructure to identify hadronically decaying top quarks using large-radius jets and evaluating the background expectation from data. No significant deviation from the background prediction is observed. Limits are set on the production cross-section times branching fraction for the new Z′ boson in a topcolor-assisted-technicolor model. The Z′ boson masses below 3.9 and 4.7 TeV are excluded at 95% confidence level for the decay widths of 1% and 3%, respectively. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 173. |
- Aad, G, et al.
(författare)
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Search for type-III seesaw heavy leptons in dilepton final states in pp collisions at √s=13TeV with the ATLAS detector
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:3
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Tidskriftsartikel (refereegranskat)abstract
- A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139fb-1 of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy leptons is 790 GeV at 95% confidence level. © 2021, CERN for the benefit of the ATLAS collaboration.
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| 174. |
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| 175. |
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| 176. |
- Aad, G, et al.
(författare)
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Searches for lepton-flavour-violating decays of the Higgs boson in s=13 TeV pp collisions with the ATLAS detector
- 2020
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 800
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Tidskriftsartikel (refereegranskat)abstract
- This Letter presents direct searches for lepton flavour violation in Higgs boson decays, H→eτ and H→μτ, performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton–proton collisions at a centre-of-mass energy s=13 TeV, corresponding to an integrated luminosity of 36.1 fb−1. No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95% confidence-level upper limits on the lepton-flavour-violating branching ratios are 0.47% (0.34−0.10 +0.13%) and 0.28% (0.37−0.10 +0.14%) for H→eτ and H→μτ, respectively. © 2019 The Author(s)
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| 177. |
- Aad, G., et al.
(författare)
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Searches for lepton-flavour-violating decays of the Higgs boson into eτ and μτ in √s=13 TeV pp collisions with the ATLAS detector
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2023:7
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents direct searches for lepton flavour violation in Higgs boson decays, H → eτ and H → μτ, performed using data collected with the ATLAS detector at the LHC. The searches are based on a data sample of proton-proton collisions at a centre-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 138 fb−1. Leptonic (τ → ℓνℓντ) and hadronic (τ → hadrons ντ) decays of the τ-lepton are considered. Two background estimation techniques are employed: the MC-template method, based on data-corrected simulation samples, and the Symmetry method, based on exploiting the symmetry between electrons and muons in the Standard Model backgrounds. No significant excess of events is observed and the results are interpreted as upper limits on lepton-flavour-violating branching ratios of the Higgs boson. The observed (expected) upper limits set on the branching ratios at 95% confidence level, B(H → eτ) < 0.20% (0.12%) and B(H → μτ ) < 0.18% (0.09%), are obtained with the MC-template method from a simultaneous measurement of potential H → eτ and H → μτ signals. The best-fit branching ratio difference, B(H → μτ) → B(H → eτ), measured with the Symmetry method in the channel where the τ-lepton decays to leptons, is (0.25 ± 0.10)%, compatible with a value of zero within 2.5σ.
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| 178. |
- Aad, G., et al.
(författare)
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Studies of the performance of the ATLAS detector using cosmic-ray muons
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:3
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Tidskriftsartikel (refereegranskat)abstract
- Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
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| 179. |
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| 180. |
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