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Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clement, C., . . . Zwalinski, L. (2024). A precise measurement of the Z-boson double-differential transverse momentum and rapidity distributions in the full phase space of the decay leptons with the ATLAS experiment at s=8 TeV. European Physical Journal C, 84(3), Article ID 315.
Open this publication in new window or tab >>A precise measurement of the Z-boson double-differential transverse momentum and rapidity distributions in the full phase space of the decay leptons with the ATLAS experiment at s=8 TeV
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2024 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 84, no 3, article id 315Article in journal (Refereed) Published
Abstract [en]

This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. This is in contrast to the many previous precise unfolded measurements performed in the fiducial phase space of the decay leptons. The measurement is obtained from proton–proton collision data collected by the ATLAS experiment in 2012 at s=8 TeV at the LHC and corresponding to an integrated luminosity of 20.2 fb-1. The results, based on a total of 15.3 million Z-boson decays to electron and muon pairs, extend and improve a previous measurement of the full set of angular coefficients describing Z-boson decay. The double-differential cross-section distributions in Z-boson transverse momentum pT and rapidity y are measured in the pole region, defined as 80<mℓℓ<100 GeV, over the range |y|<3.6. The total uncertainty of the normalised cross-section measurements in the peak region of the pT distribution is dominated by statistical uncertainties over the full range and increases as a function of rapidity from 0.5–1.0% for |y|<2.0 to 2-7% at higher rapidities. The results for the rapidity-dependent transverse momentum distributions are compared to state-of-the-art QCD predictions, which combine in the best cases approximate N4LL resummation with N3LO fixed-order perturbative calculations. The differential rapidity distributions integrated over pT are even more precise, with accuracies from 0.2–0.3% for |y|<2.0 to 0.4–0.9% at higher rapidities, and are compared to fixed-order QCD predictions using the most recent parton distribution functions. The agreement between data and predictions is quite good in most cases.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-235978 (URN)10.1140/epjc/s10052-024-12438-w (DOI)001253017600003 ()2-s2.0-85190755857 (Scopus ID)
Available from: 2024-11-26 Created: 2024-11-26 Last updated: 2024-11-26Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Bohm, C., Clément, C., Dunne, K., . . . Zwalinski, L. (2024). Accuracy versus precision in boosted top tagging with the ATLAS detector. Journal of Instrumentation, 19(8), Article ID P08018.
Open this publication in new window or tab >>Accuracy versus precision in boosted top tagging with the ATLAS detector
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2024 (English)In: Journal of Instrumentation, E-ISSN 1748-0221, Vol. 19, no 8, article id P08018Article in journal (Refereed) Published
Abstract [en]

The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.

Keywords
Analysis and statistical methods, Performance of High Energy Physics Detectors
National Category
Accelerator Physics and Instrumentation Subatomic Physics
Identifiers
urn:nbn:se:su:diva-238071 (URN)10.1088/1748-0221/19/08/P08018 (DOI)001381766600001 ()2-s2.0-85203388592 (Scopus ID)
Available from: 2025-01-27 Created: 2025-01-27 Last updated: 2025-01-27Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV Pb+Pb and 𝑝⁢𝑝 Collisions with the ATLAS Detector. Physical Review Letters, 132(20), Article ID 202301.
Open this publication in new window or tab >>Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV Pb+Pb and 𝑝⁢𝑝 Collisions with the ATLAS Detector
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2024 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 20, article id 202301Article in journal (Refereed) Published
Abstract [en]

Angular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb+Pb and 𝑝⁢𝑝 collisions at the LHC. The muons are measured with transverse momenta and pseudorapidities satisfying and |𝜂𝜇|<2.4, respectively. The distributions of azimuthal angle separation Δ⁢𝜙 for muon pairs having pseudorapidity separation |Δ⁢𝜂|>0.8, are measured in different Pb +Pb centrality intervals and compared to the same distribution measured in 𝑝⁢𝑝 collisions at the same center-of-mass energy. Results are presented separately for muon pairs with opposite-sign charges, same-sign charges, and all pairs. A clear peak is observed in all Δ⁢𝜙 distributions at Δ⁢𝜙∼𝜋, consistent with the parent heavy-quark pairs being produced via hard-scattering processes. The widths of that peak, characterized using Cauchy-Lorentz fits to the Δ⁢𝜙 distributions, are found to not vary significantly as a function of Pb +Pb collision centrality and are similar for 𝑝⁢𝑝 and Pb +Pb collisions. This observation will provide important constraints on theoretical descriptions of heavy-quark interactions with the quark-gluon plasma.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-235780 (URN)10.1103/PhysRevLett.132.202301 (DOI)001271839000001 ()38829073 (PubMedID)2-s2.0-85193942982 (Scopus ID)
Available from: 2024-11-25 Created: 2024-11-25 Last updated: 2024-11-25Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Bohm, C., Clément, C., Dunne, K., . . . Zwalinski, L. (2024). Calibration of a soft secondary vertex tagger using proton-proton collisions at √𝑠 =13  TeV with the ATLAS detector. Physical Review D: covering particles, fields, gravitation, and cosmology, 110(3), Article ID 032015.
Open this publication in new window or tab >>Calibration of a soft secondary vertex tagger using proton-proton collisions at √𝑠 =13  TeV with the ATLAS detector
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2024 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 110, no 3, article id 032015Article in journal (Refereed) Published
Abstract [en]

Several processes studied by the ATLAS experiment at the Large Hadron Collider produce low-momentum 𝑏-flavored hadrons in the final state. This paper describes the calibration of a dedicated tagging algorithm that identifies 𝑏-flavored hadrons outside of hadronic jets by reconstructing the soft secondary vertices originating from their decays. The calibration is based on a proton-proton collision dataset at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 140  fb−1. Scale factors used to correct the algorithm’s performance in simulated events are extracted for the 𝑏-tagging efficiency and the mistag rate of the algorithm using a data sample enriched in events. Several orthogonal measurement regions are defined, binned as a function of the multiplicities of soft secondary vertices and jets containing a 𝑏-flavored hadron in the event. The mistag rate scale factors are estimated separately for events with low and high average numbers of interactions per bunch crossing. The results, which are derived from events with low missing transverse momentum, are successfully validated in a phase space characterized by high missing transverse momentum and therefore are applicable to new physics searches carried out in either phase space regime.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-238073 (URN)10.1103/PhysRevD.110.032015 (DOI)001375636400001 ()2-s2.0-85203189338 (Scopus ID)
Available from: 2025-01-21 Created: 2025-01-21 Last updated: 2025-01-21Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Combination and summary of ATLAS dark matter searches interpreted in a 2HDM with a pseudo-scalar mediator using 139 fb−1 of  √s = 13 TeV pp collision data. Science Bulletin, 69(19), 3005-3035
Open this publication in new window or tab >>Combination and summary of ATLAS dark matter searches interpreted in a 2HDM with a pseudo-scalar mediator using 139 fb−1 of  √s = 13 TeV pp collision data
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2024 (English)In: Science Bulletin, ISSN 2095-9273, Vol. 69, no 19, p. 3005-3035Article in journal (Refereed) Published
Abstract [en]

Results from a wide range of searches targeting different experimental signatures with and without missing transverse momentum (ETmiss) are used to constrain a Two-Higgs-Doublet Model (2HDM) with an additional pseudo-scalar mediating the interaction between ordinary and dark matter (2HDM+a). The analyses use up to 139 fb−1 of proton–proton collision data at a centre-of-mass energy s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider during 2015–2018. The results from three of the most sensitive searches are combined statistically. These searches target signatures with large ETmiss and a leptonically decaying Z boson; large ETmiss and a Higgs boson decaying to bottom quarks; and production of charged Higgs bosons in final states with top and bottom quarks, respectively. Constraints are derived for several common and new benchmark scenarios in the 2HDM+a.

Keywords
Beyond Standard Model, Dark matter, High-energy physics, Proton-proton
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-237195 (URN)10.1016/j.scib.2024.06.003 (DOI)2-s2.0-85202659550 (Scopus ID)
Available from: 2025-01-16 Created: 2025-01-16 Last updated: 2025-01-16Bibliographically approved
Hayrapetyan, A., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at √𝑠 =7 and 8 TeV. Physical Review Letters, 132(26), Article ID 261902.
Open this publication in new window or tab >>Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at √𝑠 =7 and 8 TeV
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2024 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 26, article id 261902Article in journal (Refereed) Published
Abstract [en]

A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and 20  fb−1 of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak 𝑡 channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is 𝑚𝑡=172.52±0.14⁢(stat)±0.30⁢(syst)  GeV, with a total uncertainty of 0.33 GeV.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-238605 (URN)10.1103/PhysRevLett.132.261902 (DOI)001290703200001 ()2-s2.0-85197696145 (Scopus ID)
Available from: 2025-01-31 Created: 2025-01-31 Last updated: 2025-01-31Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Bohm, C., Clément, C., Dunne, K., . . . Zwalinski, L. (2024). Combination of searches for Higgs boson decays into a photon and a massless dark photon using pp collisions at √s = 13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2024(8), Article ID 153.
Open this publication in new window or tab >>Combination of searches for Higgs boson decays into a photon and a massless dark photon using pp collisions at √s = 13 TeV with the ATLAS detector
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2024 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2024, no 8, article id 153Article in journal (Refereed) Published
Abstract [en]

A combination of searches for Higgs boson decays into a visible photon and a massless dark photon (H → γγd) is presented using 139 fb1 of proton-proton collision data at a centre-of-mass energy of √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on the Standard Model Higgs boson decay branching ratio is determined to be B(H → γγd) < 1.3% (1.5)%. The search is also sensitive to higher-mass Higgs bosons decaying into the same final state. The observed (expected) 95% confidence level limit on the cross-section times branching ratio ranges from 16 fb (20 fb) for mH = 400 GeV to 1.0 fb (1.5 fb) for mH = 3 TeV. Results are also interpreted in the context of a minimal simplified model.

Keywords
Hadron-Hadron Scattering, Higgs Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-238080 (URN)10.1007/JHEP08(2024)153 (DOI)2-s2.0-85202495770 (Scopus ID)
Available from: 2025-01-20 Created: 2025-01-20 Last updated: 2025-01-20Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Bohm, C., Clément, C., Dunne, K., . . . Zwalinski, L. (2024). Combination of searches for pair-produced leptoquarks at √𝑠 = 13 TeVwith the ATLAS detector. Physics Letters B, 854, Article ID 138736.
Open this publication in new window or tab >>Combination of searches for pair-produced leptoquarks at √𝑠 = 13 TeVwith the ATLAS detector
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2024 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 854, article id 138736Article in journal (Refereed) Published
Abstract [en]

A statistical combination of various searches for pair-produced leptoquarks is presented, using the full LHC Run 2 (2015–2018) data set of 139 fb−1 collected with the ATLAS detector from proton–proton collisions at a centre-of-mass energy of s=13 TeV. All possible decays of the leptoquarks into quarks of the third generation and charged or neutral leptons of any generation are investigated. Since no significant deviations from the Standard Model expectation are observed in any of the individual analyses, combined exclusion limits are set on the production cross-sections for scalar and vector leptoquarks. The resulting lower bounds on leptoquark masses exceed those from the individual analyses by up to 100 GeV, depending on the signal hypothesis.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-235610 (URN)10.1016/j.physletb.2024.138736 (DOI)001278843700001 ()2-s2.0-85194415100 (Scopus ID)
Available from: 2024-11-27 Created: 2024-11-27 Last updated: 2024-11-27Bibliographically approved
Filmer, E. K., Lou, X., Andrean, S. Y., Backman, F., Bohm, C., Clement, C., . . . Tipton, P. (2024). Combination of Searches for Resonant Higgs Boson Pair Production Using 𝑝⁢𝑝 Collisions at √𝑠=13 TeV with the ATLAS Detector. Physical Review Letters, 132(23), Article ID 231801.
Open this publication in new window or tab >>Combination of Searches for Resonant Higgs Boson Pair Production Using 𝑝⁢𝑝 Collisions at √𝑠=13 TeV with the ATLAS Detector
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2024 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 23, article id 231801Article in journal (Refereed) Published
Abstract [en]

A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to Formula Presented of Formula Presented collision data at Formula Presented recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: Formula Presented, Formula Presented, and Formula Presented. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches.

National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:su:diva-235521 (URN)10.1103/PhysRevLett.132.231801 (DOI)38905640 (PubMedID)2-s2.0-85196005989 (Scopus ID)
Available from: 2024-11-14 Created: 2024-11-14 Last updated: 2024-11-14Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Deep Generative Models for Fast Photon Shower Simulation in ATLAS. Computing and Software for Big Science, 8(1), Article ID 7.
Open this publication in new window or tab >>Deep Generative Models for Fast Photon Shower Simulation in ATLAS
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2024 (English)In: Computing and Software for Big Science, ISSN 2510-2036, Vol. 8, no 1, article id 7Article in journal (Refereed) Published
Abstract [en]

The need for large-scale production of highly accurate simulated event samples for the extensive physics programme of the ATLAS experiment at the Large Hadron Collider motivates the development of new simulation techniques. Building on the recent success of deep learning algorithms, variational autoencoders and generative adversarial networks are investigated for modelling the response of the central region of the ATLAS electromagnetic calorimeter to photons of various energies. The properties of synthesised showers are compared with showers from a full detector simulation using ɢᴇᴀɴᴛ4. Both variational autoencoders and generative adversarial networks are capable of quickly simulating electromagnetic showers with correct total energies and stochasticity, though the modelling of some shower shape distributions requires more refinement. This feasibility study demonstrates the potential of using such algorithms for ATLAS fast calorimeter simulation in the future and shows a possible way to complement current simulation techniques.

National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:su:diva-235486 (URN)10.1007/s41781-023-00106-9 (DOI)2-s2.0-85189330049 (Scopus ID)
Available from: 2024-11-15 Created: 2024-11-15 Last updated: 2024-11-15Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7253-7497

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