| 1. |
- G., Aad, et al.
(författare)
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Electron and photon performance measurements with the ATLAS detector using the 2015-2017 LHC proton-proton collision data
- 2019
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the reconstruction of electrons and photons with the ATLAS detector, employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb-1 of proton-proton collision data collected at √s = 13 TeV between 2015 and 2017. © 2019 CERN for the benefit of the ATLAS collaboration. Published by IOP Publishing Ltd on behalf of Sissa Medialab.
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| 2. |
- G., Aad, et al.
(författare)
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Measurement of the cross-section and charge asymmetry of W bosons produced in proton–proton collisions at √s=8TeV with the ATLAS detector
- 2019
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 79:9
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents measurements of the W+→ μ+ν and W-→ μ-ν cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton–proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2fb-1. The precision of the cross-section measurements varies between 0.8 and 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them. © 2019, CERN for the benefit of the ATLAS collaboration.
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| 3. |
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| 4. |
- G., Aad, et al.
(författare)
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Search for a heavy charged boson in events with a charged lepton and missing transverse momentum from pp collisions at s =13 TeV with the ATLAS detector
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:5
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Tidskriftsartikel (refereegranskat)abstract
- A search for a heavy charged-boson resonance decaying into a charged lepton (electron or muon) and a neutrino is reported. A data sample of 139 fb-1 of proton-proton collisions at s=13 TeV collected with the ATLAS detector at the LHC during 2015-2018 is used in the search. The observed transverse mass distribution computed from the lepton and missing transverse momenta is consistent with the distribution expected from the Standard Model, and upper limits on the cross section for pp→W′→ℓν are extracted (ℓ=e or μ). These vary between 1.3 pb and 0.05 fb depending on the resonance mass in the range between 0.15 and 7.0 TeV at 95% confidence level for the electron and muon channels combined. Gauge bosons with a mass below 6.0 and 5.1 TeV are excluded in the electron and muon channels, respectively, in a model with a resonance that has couplings to fermions identical to those of the Standard Model W boson. Cross-section limits are also provided for resonances with several fixed Γ/m values in the range between 1% and 15%. Model-independent limits are derived in single-bin signal regions defined by a varying minimum transverse mass threshold. The resulting visible cross-section upper limits range between 4.6 (15) pb and 22 (22) ab as the threshold increases from 130 (110) GeV to 5.1 (5.1) TeV in the electron (muon) channel. © 2019 CERN. © 2019 CERN, for the ATLAS Collaboration.
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| 5. |
- G., Aad, et al.
(författare)
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Search for electroweak diboson production in association with a high-mass dijet system in semileptonic final states in pp collisions at s =13 TeV with the ATLAS detector
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a search for electroweak diboson (WW/WZ/ZZ) production in association with a high-mass dijet system, using data from proton-proton collisions at a center-of-mass energy of s=13 TeV. The data, corresponding to an integrated luminosity of 35.5 fb-1, were recorded with the ATLAS detector in 2015 and 2016 at the Large Hadron Collider. The search is performed in final states in which one boson decays leptonically, and the other boson decays hadronically. The hadronically decaying W/Z boson is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. The electroweak production of WW/WZ/ZZ in association with two jets is measured with an observed (expected) significance of 2.7 (2.5) standard deviations, and the fiducial cross section is measured to be 45.1±8.6(stat.)-14.6+15.9(syst.) fb. © 2019 CERN.
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| 6. |
- Milstead, David A., et al.
(författare)
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Combination of Searches for Invisible Higgs Boson Decays with the ATLAS Experiment
- 2019
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 122:23
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Tidskriftsartikel (refereegranskat)abstract
- Dark matter particles, if sufficiently light, may be produced in decays of the Higgs boson. This Letter presents a statistical combination of searches for H→invisible decays where H is produced according to the standard model via vector boson fusion, Z(-)H, and W/Z(had)H, all performed with the ATLAS detector using 36.1 fb-1 of pp collisions at a center-of-mass energy of s=13 TeV at the LHC. In combination with the results at s=7 and 8 TeV, an exclusion limit on the H→invisible branching ratio of 0.26(0.17-0.05+0.07) at 95% confidence level is observed (expected). © 2019 CERN.
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| 7. |
- Milstead, David A., et al.
(författare)
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Electron reconstruction and identification in the ATLAS experiment using the 2015 and 2016 LHC proton–proton collision data at √s=13 TeV
- 2019
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 79:8
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Tidskriftsartikel (refereegranskat)abstract
- Algorithms used for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC) are presented in this paper; these algorithms are used in ATLAS physics analyses that involve electrons in the final state and which are based on the 2015 and 2016 proton–proton collision data produced by the LHC at s = 13 TeV. The performance of the electron reconstruction, identification, isolation, and charge identification algorithms is evaluated in data and in simulated samples using electrons from Z→ ee and J/ ψ→ ee decays. Typical examples of combinations of electron reconstruction, identification, and isolation operating points used in ATLAS physics analyses are shown. © 2019, CERN for the benefit of the ATLAS collaboration.
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| 8. |
- Milstead, David A., et al.
(författare)
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Search for heavy particles decaying into a top-quark pair in the fully hadronic final state in pp collisions at s =13 TeV with the ATLAS detector
- 2019
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 99:9
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Tidskriftsartikel (refereegranskat)abstract
- A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of s=13 TeV corresponding to an integrated luminosity of 36.1 fb-1. Events consistent with top-quark pair production and the fully hadronic decay mode of the top quarks are selected by requiring multiple high transverse momentum jets including those containing b-hadrons. Two analysis techniques, exploiting dedicated top-quark pair reconstruction in different kinematic regimes, are used to optimize the search sensitivity to new hypothetical particles over a wide mass range. The invariant mass distribution of the two reconstructed top-quark candidates is examined for resonant production of new particles with various spins and decay widths. No significant deviation from the Standard Model prediction is observed and limits are set on the production cross-section times branching fraction for new hypothetical Z′ bosons, dark-matter mediators, Kaluza-Klein gravitons and Kaluza-Klein gluons. By comparing with the predicted production cross sections, the Z′ boson in the topcolor-assisted-technicolor model is excluded for masses up to 3.1-3.6 TeV, the dark-matter mediators in a simplified framework are excluded in the mass ranges from 0.8 to 0.9 TeV and from 2.0 to 2.2 TeV, and the Kaluza-Klein gluon is excluded for masses up to 3.4 TeV, depending on the decay widths of the particles. © 2019 CERN, for the ATLAS Collaboration.
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| 9. |
- Milstead, David A., et al.
(författare)
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Cross-section measurements of the Higgs boson decaying into a pair of τ -leptons in proton-proton collisions at s =13 TeV with the ATLAS detector
- 2019
-
Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 99:7
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of production cross sections of the Higgs boson in proton-proton collisions is presented in the H→ττ decay channel. The analysis is performed using 36.1 fb-1 of data recorded by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy of s=13 TeV. All combinations of leptonic (τ→vv with =e,μ) and hadronic (τ→hadrons v) τ decays are considered. The H→ττ signal over the expected background from other Standard Model processes is established with an observed (expected) significance of 4.4 (4.1) standard deviations. Combined with results obtained using data taken at 7 and 8 TeV center-of-mass energies, the observed (expected) significance amounts to 6.4 (5.4) standard deviations and constitutes an observation of H→ττ decays. Using the data taken at s=13 TeV, the total cross section in the H→ττ decay channel is measured to be 3.77-0.59+0.60 (stat) -0.74+0.87 (syst) pb, for a Higgs boson of mass 125 GeV assuming the relative contributions of its production modes as predicted by the Standard Model. Total cross sections in the H→ττ decay channel are determined separately for vector-boson-fusion production and gluon-gluon-fusion production to be σH→ττVBF=0.28±0.09 (stat) -0.09+0.11 (syst) pb and σH→ττggF=3.1±1.0 (stat) -1.3+1.6 (syst) pb, respectively. Similarly, results of a fit are reported in the framework of simplified template cross sections. All measurements are in agreement with Standard Model expectations. © 2019 CERN, for the ATLAS Collaboration.
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| 10. |
- Milstead, David A., et al.
(författare)
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Search for long-lived particles in final states with displaced dimuon vertices in pp collisions at s =13 TeV with the ATLAS detector
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 99:1
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Tidskriftsartikel (refereegranskat)abstract
- A search is performed for a long-lived particle decaying into a final state that includes a pair of muons of opposite-sign electric charge, using proton-proton collision data collected at s=13 TeV by the ATLAS detector at the Large Hadron Collider corresponding to an integrated luminosity of 32.9 fb-1. No significant excess over the Standard Model expectation is observed. Limits at 95% confidence level on the lifetime of the long-lived particle are presented in models of new phenomena including gauge-mediated supersymmetry or decay of the Higgs boson, H, to a pair of dark photons, ZD. Lifetimes in the range cτ=1-2400 cm are excluded, depending on the parameters of the model. In the supersymmetric model, the lightest neutralino is the next-to-lightest supersymmetric particle, with a relatively long lifetime due to its weak coupling to the gravitino, the lightest supersymmetric particle. The lifetime limits are determined for very light gravitino mass and various assumptions for the neutralino mass in the range 300-1000 GeV. In the dark photon model, the lifetime limits are interpreted as exclusion contours in the plane of the coupling between the ZD and the Standard Model Z boson versus the ZD mass (in the range 20-60 GeV), for various assumptions for the H→ZDZD branching fraction. © 2019 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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