| 131. |
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| 132. |
- Aad, G, et al.
(författare)
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Search for Higgs Boson Decays into a Z Boson and a Light Hadronically Decaying Resonance Using 13 TeV pp Collision Data from the ATLAS Detector
- 2020
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 1079-7114 .- 0031-9007. ; 125:22
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Tidskriftsartikel (refereegranskat)abstract
- A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139 fb-1 collected at s=13 TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar sector or a charmonium state. Multivariate discriminants are used for the event selection and for evaluating the mass of the light resonance. No excess of events above the expected background is found. Observed (expected) 95% confidence-level upper limits are set on the Higgs boson production cross section times branching fraction to a Z boson and the signal resonance, with values in the range 17-340 pb (16-5+6-320-90+130 pb) for the different light spin-0 boson mass and branching fraction hypotheses, and with values of 110 and 100 pb (100-30+40 and 100-30+40 pb) for the ηc and J/ψ hypotheses, respectively. © 2020 CERN. © 2020 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.
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| 133. |
- Aad, G, et al.
(författare)
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Search for Higgs boson decays into two new low-mass spin-0 particles in the 4b channel with the ATLAS detector using pp collisions at s =13 TeV
- 2020
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Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 102:11
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into b-quark pairs, H→aa→(bb¯)(bb¯), using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy s=13 TeV. This search focuses on the range 15 GeV≤ma≤30 GeV, where the decay products are collimated; it is complementary to a previous search in the same final state targeting the range 20 GeV≤ma≤60 GeV, where the decay products are well separated. A novel strategy for the identification of the a→bb¯ decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb-1 of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross section of H→aa→(bb¯)(bb¯), where the Higgs boson is produced in association with a Z boson. © 2020 CERN.
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| 134. |
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| 135. |
- Aad, G, et al.
(författare)
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Search for high-mass dilepton resonances using 139 fb−1 of pp collision data collected at s=13 TeV with the ATLAS detector
- 2019
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 796, s. 68-87
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Tidskriftsartikel (refereegranskat)abstract
- A search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV is presented. The data were recorded by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of s=13 TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb−1. A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes, and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses. The derived limits are shown to be applicable to spin-0, spin-1 and spin-2 signal hypotheses. For a set of benchmark models, the limits are converted into lower limits on the resonance mass and reach 4.5 TeV for the E6-motivated Zψ ′ boson. Also presented are limits on Heavy Vector Triplet model couplings.
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| 136. |
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| 137. |
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| 138. |
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| 139. |
- Aad, G., et al.
(författare)
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Search for leptonic charge asymmetry in tt¯W production in final states with three leptons at √s = 13 TeV
- 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
- A search for the leptonic charge asymmetry () of top-quark-antiquark pair production in association with a W boson () is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on √s = 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015–2018, corresponding to an integrated luminosity of 139 fb−1. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be −0.12 ± 0.14 (stat.) ± 0.05 (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of −0.11 ± 0.17 (stat.) ± 0.05 (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are (scale) ± 0.006 (MC stat.) and (scale) ± 0.004 (MC stat.) respectively, and in agreement with the measurements.
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| 140. |
- Aad, G., et al.
(författare)
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Search for leptoquarks decaying into the bτ final state in pp collisions at √s=13 TeV with the ATLAS detector
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2023:10
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Tidskriftsartikel (refereegranskat)abstract
- A search for leptoquarks decaying into the bτ final state is performed using Run 2 proton-proton collision data from the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1 at √s = 13 TeV recorded by the ATLAS detector. The benchmark models considered in this search are vector leptoquarks with electric charge of 2/3e and scalar leptoquarks with an electric charge of 4/3e. No significant excess above the Standard Model prediction is observed, and 95% confidence level upper limits are set on the cross-section times branching fraction of leptoquarks decaying into bτ. For the vector leptoquark production two models are considered: the Yang-Mills and Minimal coupling models. In the Yang-Mills (Minimal coupling) scenario, vector leptoquarks with a mass below 1.58 (1.35) TeV are excluded for a gauge coupling of 1.0 and below 2.05 (1.99) TeV for a gauge coupling of 2.5. In the case of scalar leptoquarks, masses below 1.28 (1.53) TeV are excluded for a Yukawa coupling of 1.0 (2.5). Finally, an interpretation of the results with minimal model dependence is performed for each of the signal region categories, and limits on the visible cross-section for beyond the Standard Model processes are provided.
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