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Publications (10 of 615) Show all publications
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Search for quantum black hole production in lepton+jet final states using proton-proton collisions at √s=13 TeV with the ATLAS detector. Physical Review D: covering particles, fields, gravitation, and cosmology, 109(3), Article ID 032010.
Open this publication in new window or tab >>Search for quantum black hole production in lepton+jet final states 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. 109, no 3, article id 032010Article in journal (Refereed) Published
Abstract [en]

A search for quantum black holes in electron+jet and muon+jet invariant mass spectra is performed with 140  fb−1 of data collected by the ATLAS detector in proton-proton collisions at √s=13  TeV at the Large Hadron Collider. The observed invariant mass spectrum of lepton+jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-227769 (URN)10.1103/PhysRevD.109.032010 (DOI)001183228500014 ()2-s2.0-85187155078 (Scopus ID)
Available from: 2024-04-08 Created: 2024-04-08 Last updated: 2024-04-08Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at √s=13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2023(7), Article ID 200.
Open this publication in new window or tab >>A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at √s=13 TeV with the ATLAS detector
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 7, article id 200Article in journal (Refereed) Published
Abstract [en]

A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton–proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb−1. The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson’s mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.

Keywords
Higgs Physics, Hadron-Hadron Scattering, Proton-Proton Scattering
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-223271 (URN)10.1007/JHEP07(2023)200 (DOI)001061852200001 ()
Available from: 2023-10-26 Created: 2023-10-26 Last updated: 2023-10-26Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at √s=7 and 8 TeV. Journal of High Energy Physics (JHEP), 2023(7), Article ID 213.
Open this publication in new window or tab >>Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at √s=7 and 8 TeV
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 7, article id 213Article in journal (Refereed) Published
Abstract [en]

A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb−1 at √s = 7 TeV and about 20 fb−1 at √s = 8 TeV for each experiment. The combined cross-sections are determined to be 178.5 ± 4.7 pb at √s = 7 TeV and pb at √s = 8 TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections is determined to be R8/7 = 1.363 ± 0.032. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are = GeV and αs(mZ)=.

Keywords
Hadron-Hadron Scattering, Top Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-224205 (URN)10.1007/JHEP07(2023)213 (DOI)001058564200001 ()
Available from: 2023-12-06 Created: 2023-12-06 Last updated: 2023-12-06Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV pp collision data with two top quarks and missing transverse momentum in the final state. European Physical Journal C, 83(6), Article ID 503.
Open this publication in new window or tab >>Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV pp collision data with two top quarks and missing transverse momentum in the final state
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2023 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 6, article id 503Article in journal (Refereed) Published
Abstract [en]

This paper presents a statistical combination of searches targeting final states with two top quarks and invisible particles, characterised by the presence of zero, one or two leptons, at least one jet originating from a b-quark and missing transverse momentum. The analyses are searches for phenomena beyond the Standard Model consistent with the direct production of dark matter in pp collisions at the LHC, using 139 fb−1 of data collected with the ATLAS detector at a centre-of-mass energy of 13 TeV. The results are interpreted in terms of simplified dark matter models with a spin-0 scalar or pseudoscalar mediator particle. In addition, the results are interpreted in terms of upper limits on the Higgs boson invisible branching ratio, where the Higgs boson is produced according to the Standard Model in association with a pair of top quarks. For scalar (pseudoscalar) dark matter models, with all couplings set to unity, the statistical combination extends the mass range excluded by the best of the individual channels by 50 (25) GeV, excluding mediator masses up to 370 GeV. In addition, the statistical combination improves the expected coupling exclusion reach by 14% (24%), assuming a scalar (pseudoscalar) mediator mass of 10 GeV. An upper limit on the Higgs boson invisible branching ratio of 0.38 () is observed (expected) at 95% confidence level.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-228215 (URN)10.1140/epjc/s10052-023-11477-z (DOI)001187459300004 ()2-s2.0-85164130040 (Scopus ID)
Available from: 2024-04-15 Created: 2024-04-15 Last updated: 2024-04-15Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Correlations between flow and transverse momentum in Xe+Xe and Pb+Pb collisions at the LHC with the ATLAS detector: A probe of the heavy-ion initial state and nuclear deformation. Physical Review C: Covering Nuclear Physics, 107(5), Article ID 054910.
Open this publication in new window or tab >>Correlations between flow and transverse momentum in Xe+Xe and Pb+Pb collisions at the LHC with the ATLAS detector: A probe of the heavy-ion initial state and nuclear deformation
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2023 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 107, no 5, article id 054910Article in journal (Refereed) Published
Abstract [en]

The correlations between flow harmonics vn for n=2, 3, and 4 and mean transverse momentum [pT] in 129Xe+129Xe and 208Pb+208Pb collisions at √s=5.44 and 5.02 TeV, respectively, are measured using charged particles with the ATLAS detector. The correlations are potentially sensitive to the shape and size of the initial geometry, nuclear deformation, and initial momentum anisotropy. The effects from nonflow and centrality fluctuations are minimized, respectively, via a subevent cumulant method and an event-activity selection based on particle production at very forward rapidity. The vn−[pT] correlations show strong dependencies on centrality, harmonic number n, pT, and pseudorapidity range. Current models qualitatively describe the overall centrality- and system-dependent trends but fail to quantitatively reproduce all features of the data. In central collisions, where models generally show good agreement, the v2−[pT] correlations are sensitive to the triaxiality of the quadruple deformation. Comparison of the model with the Pb+Pb and Xe+Xe data confirms that the 129Xe nucleus is a highly deformed triaxial ellipsoid that has neither a prolate nor oblate shape. This provides strong evidence for a triaxial deformation of the 129Xe nucleus from high-energy heavy-ion collisions.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-221773 (URN)10.1103/PhysRevC.107.054910 (DOI)001021700000001 ()2-s2.0-85164169793 (Scopus ID)
Available from: 2023-10-03 Created: 2023-10-03 Last updated: 2023-10-03Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Cross-section measurements for the production of a Z boson in association with high-transverse-momentum jets in pp collisions at √s = 13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2023(6), Article ID 80.
Open this publication in new window or tab >>Cross-section measurements for the production of a Z boson in association with high-transverse-momentum jets in pp collisions at √s = 13 TeV with the ATLAS detector
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 6, article id 80Article in journal (Refereed) Published
Abstract [en]

Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets (pT ≥ 100 GeV) and decaying into a charged-lepton pair (e+e, μ+μ) are presented. The measurements are performed using proton–proton collisions at √s = 13 TeV corresponding to an integrated luminosity of 139 fb−1 collected by the ATLAS experiment at the LHC. Measurements of angular correlations between the Z boson and the closest jet are performed in events with at least one jet with pT ≥ 500 GeV. Event topologies of particular interest are the collinear emission of a Z boson in dijet events and a boosted Z boson recoiling against a jet. Fiducial cross sections are compared with state-of-the-art theoretical predictions. The data are found to agree with next-to-next-to-leading-order predictions by NNLOᴊᴇᴛ and with the next-to-leading-order multi-leg generators MADGRAPH5_AMC@NLO and SHERPA.

Keywords
Electroweak Interaction, Hadron-Hadron Scattering
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-221775 (URN)10.1007/JHEP06(2023)080 (DOI)001035282400001 ()2-s2.0-85163163392 (Scopus ID)
Available from: 2023-10-03 Created: 2023-10-03 Last updated: 2023-10-03Bibliographically approved
Aad, G., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., Hellman, S., . . . Zwalinski, L. (2023). Determination of the strong coupling constant from transverse energy-energy correlations in multijet events at √ s=13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2023(7), Article ID 085.
Open this publication in new window or tab >>Determination of the strong coupling constant from transverse energy-energy correlations in multijet events at √ s=13 TeV with the ATLAS detector
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 7, article id 085Article in journal (Refereed) Published
Abstract [en]

Measurements of transverse energy-energy correlations and their associated azimuthal asymmetries in multijet events are presented. The analysis is performed using a data sample corresponding to 139 fb-1 of proton-proton collisions at a centre-of-mass energy of root s = 13TeV, collected with the ATLAS detector at the Large Hadron Collider. The measurements are presented in bins of the scalar sum of the transverse momenta of the two leading jets and unfolded to particle level. They are then compared to next-to-next-to-leading-order perturbative QCD calculations for the first time, which feature a significant reduction in the theoretical uncertainties estimated using variations of the renormalisation and factorisation scales. The agreement between data and theory is good, thus providing a precision test of QCD at large momentum transfers Q. The strong coupling constant alpha(s) is extracted as a function of Q, showing a good agreement with the renormalisation group equation and with previous analyses. A simultaneous fit to all transverse energy-energy correlation distributions across different kinematic regions yields a value of alpha(s)( mZ) = 0.1175 +/- 0.0006 (exp.)(+0.0034) (-0.0017) (theo.), while the global fit to the asymmetry distributions yields alpha(s)(m(Z)) = 0.1185 +/- 0.0009 (exp.)(+0.0025)(-0.0012)(theo.).

Keywords
Hadron-Hadron Scattering, Jet Physics, Jets
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-223221 (URN)10.1007/JHEP07(2023)085 (DOI)001061751900001 ()2-s2.0-85165298184 (Scopus ID)
Available from: 2023-12-06 Created: 2023-12-06 Last updated: 2023-12-07Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Differential tt¯ cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb−1 of ATLAS data. Journal of High Energy Physics (JHEP), 2023(4), Article ID 080.
Open this publication in new window or tab >>Differential tt¯ cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb1 of ATLAS data
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 4, article id 080Article in journal (Refereed) Published
Abstract [en]

Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV proton–proton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum (pT) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have pT > 500 GeV and pT > 350 GeV, respectively, is 331 ± 3(stat.) ± 39(syst.) fb. This is approximately 20% lower than the prediction of fb by POWHEG+PYTHIA 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1.94 ± 0.02(stat.) ± 0.25(syst.) pb. This agrees with the NNLO prediction of pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators.

Keywords
Hadron-Hadron Scattering, Jet Substructure and Boosted Jets, Top Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-221779 (URN)10.1007/JHEP04(2023)080 (DOI)001022682600001 ()2-s2.0-85156104827 (Scopus ID)
Available from: 2023-10-02 Created: 2023-10-02 Last updated: 2023-10-02Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Evidence for the charge asymmetry in pp → tt- production at √s=13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2023(8), Article ID 77.
Open this publication in new window or tab >>Evidence for the charge asymmetry in pp → tt- production at √s=13 TeV with the ATLAS detector
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 8, article id 77Article in journal (Refereed) Published
Abstract [en]

Inclusive and differential measurements of the top–antitop () charge asymmetry and the leptonic asymmetry are presented in proton–proton collisions at √s = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb−1, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive charge asymmetry is measured to be = 0.0068 ± 0.0015, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.

Keywords
Hadron-Hadron Scattering, Top Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-223710 (URN)10.1007/JHEP08(2023)077 (DOI)001062398000001 ()2-s2.0-85169322582 (Scopus ID)
Available from: 2023-11-17 Created: 2023-11-17 Last updated: 2023-11-17Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2023). Exclusive dielectron production in ultraperipheral Pb+Pb collisions at √sNN=5.02 TeV with ATLAS. Journal of High Energy Physics (JHEP), 2023(6), Article ID 182.
Open this publication in new window or tab >>Exclusive dielectron production in ultraperipheral Pb+Pb collisions at √sNN=5.02 TeV with ATLAS
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2023, no 6, article id 182Article in journal (Refereed) Published
Abstract [en]

Exclusive production of dielectron pairs, γγ → e+e, is studied using = 1.72 nb−1 of data from ultraperipheral collisions of lead nuclei at √sNN = 5.02 TeV recorded by the ATLAS detector at the LHC. The process of interest proceeds via photon–photon interactions in the strong electromagnetic fields of relativistic lead nuclei. Dielectron production is measured in the fiducial region defined by following requirements: electron transverse momentum > 2.5 GeV, absolute electron pseudorapidity |ηe| < 2.5, dielectron invariant mass mee > 5 GeV, and dielectron transverse momentum < 2 GeV. Differential cross-sections are measured as a function of mee, average , absolute dielectron rapidity |yee|, and scattering angle in the dielectron rest frame, |cos θ*|, in the inclusive sample, and also with a requirement of no activity in the forward direction. The total integrated fiducial cross-section is measured to be 215±1(stat.)(syst.)±4(lumi.) μb. Within experimental uncertainties the measured integrated cross-section is in good agreement with the QED predictions from the Monte Carlo programs STARLIGHT and SUPERCHIC, confirming the broad features of the initial photon fluxes. The differential cross-sections show systematic differences from these predictions which are more pronounced at high |yee| and |cos θ*| values.

Keywords
Heavy Ion Experiments, Heavy-Ion Collision
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-223712 (URN)10.1007/JHEP06(2023)182 (DOI)001069745300005 ()2-s2.0-85163887123 (Scopus ID)
Available from: 2023-11-29 Created: 2023-11-29 Last updated: 2023-11-29Bibliographically approved
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