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Publications (10 of 27) Show all publications
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Differential cross-section measurements of the production of four charged leptons in association with two jets using the ATLAS detector. Journal of High Energy Physics (JHEP), 2024(1), Article ID 4.
Open this publication in new window or tab >>Differential cross-section measurements of the production of four charged leptons in association with two jets using 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 1, article id 4Article in journal (Refereed) Published
Abstract [en]

Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at √s = 13 TeV and with an integrated luminosity of 140 fb−1. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory.

Keywords
Hadron-Hadron Scattering
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-228229 (URN)10.1007/JHEP01(2024)004 (DOI)001184438800001 ()
Available from: 2024-04-11 Created: 2024-04-11 Last updated: 2024-04-11Bibliographically approved
Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., Dunne, K., . . . Valdés Santurio, E. (2024). Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data. Journal of Instrumentation, 19(2), Article ID P02009.
Open this publication in new window or tab >>Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data
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2024 (English)In: Journal of Instrumentation, E-ISSN 1748-0221, Vol. 19, no 2, article id P02009Article in journal (Refereed) Published
Abstract [en]

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb-1 of LHC proton-proton collision data recorded at √(s) = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ψ → ee and radiative Z-boson decays.

Keywords
Calorimeter methods, Pattern recognition, cluster finding, calibration and fitting methods, Performance of High Energy Physics Detectors
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-228655 (URN)10.1088/1748-0221/19/02/P02009 (DOI)001185791500005 ()2-s2.0-85185886671 (Scopus ID)
Available from: 2024-04-26 Created: 2024-04-26 Last updated: 2024-07-04Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zhokin, A. (2024). Evidence for the Higgs Boson Decay to a Z Boson and a Photon at the LHC. Physical Review Letters, 132(2), Article ID 021803.
Open this publication in new window or tab >>Evidence for the Higgs Boson Decay to a Z Boson and a Photon at the LHC
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2024 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 2, article id 021803Article in journal (Refereed) Published
Abstract [en]

The first evidence for the Higgs boson decay to a Z boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision datasets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140  fb−1 for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is 2.2±0.7 times the standard model prediction, and agrees with the theoretical expectation within 1.9 standard deviations.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-229031 (URN)10.1103/PhysRevLett.132.021803 (DOI)001185794500011 ()38277607 (PubMedID)2-s2.0-85182246849 (Scopus ID)
Available from: 2024-05-15 Created: 2024-05-15 Last updated: 2024-05-15Bibliographically approved
Riefel, E. M. (2024). Gauge-mediated supersymmetry breakingin the Next-to-Minimal Supersymmetric Model andcalibration of algorithms to identify bottom quarks. (Licentiate dissertation). Stockholm: Department of Physics, Stockholm University
Open this publication in new window or tab >>Gauge-mediated supersymmetry breakingin the Next-to-Minimal Supersymmetric Model andcalibration of algorithms to identify bottom quarks
2024 (English)Licentiate thesis, monograph (Other academic)
Abstract [en]

This thesis consists of two main parts. The first part presents a search strategyfor a non-minimal supersymmetric model in which supersymmetry is brokenin three hidden sectors and is mediated by gauge bosons to the visible sector.The parameter space of such a model is scanned and 138 viable benchmarkpoints are obtained that produce final states with three photons and missingtransverse energy. A signal region is optimized for this signature and upperlimits of the cross section times branching ratio for simplified models are ob-tained. These upper limits are stronger than those obtained from existingsearches. The second part of this thesis focuses on extending the jet-pT rangeof the light-jet mistag rate calibration of algorithms used to identify jets origi-nating from bottom quarks. Preliminary scale factors are presented. The scalefactors are validated by comparing them to those of the current mistag ratecalibration at lower jet-pT. A study of the effect of gluon splitting on the scalefactors has been done and it is concluded that the effect is negligible.

Abstract [sv]

Denna avhandling består av två huvuddelar. I den första delen presenteras ensökstrategi för en icke-minimal supersymmetrisk modell där supersymmetrinbryts i tre dolda sektorer och förmedlas av gaugebosoner till den synliga sek-torn. Parameterrummet för en sådan modell skannas och 138 referenspunktererhålls som producerar sluttillstånd med tre fotoner och saknad transversellenergi. En signalregion optimeras för denna signatur och övre gränser förtvärsnitt gånger förgreningskvot för förenklade modeller erhålls. Dessa övregränser är snävare än de som erhållits från befintliga sökningar. Den andra delen av denna avhandling fokuserar på att utöka jet-pT -området för kalibreringav algoritmer som utvecklas för att identifiera bottenkvarkar. Preliminäraskalfaktorer för sannolikheten att algoritmen av misstag istället väljer ut jetsfrån lättare kvarkar eller gluoner presenteras. Skalfaktorerna valideras genomatt jämföra dem med de som används i den nuvarande kalibreringen vid lägre jet-pT. En studie av effekten av bottenkvarkar producerade genom gluonemis-sion på skalfaktorerna har gjorts och slutsatsen är att effekten är försumbar.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2024. p. 80
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-229173 (URN)
Presentation
2024-06-05, C5:1007, Roslagstullsbacken 21, 10:00 (English)
Opponent
Supervisors
Available from: 2024-05-15 Created: 2024-05-15 Last updated: 2024-05-15Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Measurement of the Centrality Dependence of the Dijet Yield in p+Pb Collisions at √sNN=8.16  TeV with the ATLAS Detector. Physical Review Letters, 132(10), Article ID 102301.
Open this publication in new window or tab >>Measurement of the Centrality Dependence of the Dijet Yield in p+Pb Collisions at √sNN=8.16  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 10, article id 102301Article in journal (Refereed) Published
Abstract [en]

ATLAS measured the centrality dependence of the dijet yield using 165  nb−1 of p+Pb data collected at √sNN=8.16  TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, RCP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The RCP shows a scaling with the Bjorken x of the parton originating from the proton, xp, while no such trend is observed as a function of xPb. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to xp∼10−3 and xPb∼4×10−4.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-229030 (URN)10.1103/PhysRevLett.132.102301 (DOI)001202029400003 ()38518341 (PubMedID)2-s2.0-85187227180 (Scopus ID)
Available from: 2024-05-15 Created: 2024-05-15 Last updated: 2024-05-15Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Measurement of the H → γ γ and H → ZZ* → 4l cross-sectionsin pp collisions at √s = 13.6 TeV with the ATLAS detector. European Physical Journal C, 84(1), Article ID 78.
Open this publication in new window or tab >>Measurement of the Hγ γ and HZZ* → 4l cross-sectionsin pp collisions at √s = 13.6 TeV with the ATLAS detector
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2024 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 84, no 1, article id 78Article in journal (Refereed) Published
Abstract [en]

The inclusive Higgs boson production cross-section is measured in the di-photon and the ZZ* → 4ℓ decay channels using 31.4 and 29.0 fb−1 of pp collision data respectively, collected with the ATLAS detector at a centre-of-mass energy of √s=13.6 TeV. To reduce the model dependence, the measurement in each channel is restricted to a particle-level phase space that closely matches the channel’s detector-level kinematic selection, and it is corrected for detector effects. These measured fiducial cross-sections are σfid,γγ= fb, and σfid,4ℓ= 2.80±0.74 fb, in agreement with the corresponding Standard Model predictions of 67.6±3.7 fb and 3.67±0.19 fb. Assuming Standard Model acceptances and branching fractions for the two channels, the fiducial measurements are extrapolated to the full phase space yielding total cross-sections of σ(ppH)= pb and 46±12 pb at 13.6 TeV from the di-photon and ZZ*→ 4ℓ measurements respectively. The two measurements are combined into a total cross-section measurement of σ(ppH)=58.2±8.7 pb, to be compared with the Standard Model prediction of σ(ppH)SM=59.9±2.6 pb.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-227770 (URN)10.1140/epjc/s10052-023-12130-5 (DOI)001161543700001 ()2-s2.0-85183047904 (Scopus ID)
Available from: 2024-04-02 Created: 2024-04-02 Last updated: 2024-04-02Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Measurement of the production cross-section of J/ψ and ψ(2S) mesons in pp collisions at √s=13 TeV with the ATLAS detector. European Physical Journal C, 84(2), Article ID 169.
Open this publication in new window or tab >>Measurement of the production cross-section of J/ψ and ψ(2S) mesons in pp collisions at √s=13 TeV with the ATLAS detector
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2024 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 84, no 2, article id 169Article in journal (Refereed) Published
Abstract [en]

Measurements of the differential production cross-sections of prompt and non-prompt 𝐽/𝜓 and 𝜓(2S) mesons with transverse momenta between 8 and 360 GeV and rapidity in the range |𝑦|<2 are reported. Furthermore, measurements of the non-prompt fractions of 𝐽/𝜓 and 𝜓(2S), and the prompt and non-prompt 𝜓(2S)-to-𝐽/𝜓 production ratios, are presented. The analysis is performed using 140 fb−1 of √𝑠=13 TeV pp collision data recorded by the ATLAS detector at the LHC during the years 2015–2018.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-229029 (URN)10.1140/epjc/s10052-024-12439-9 (DOI)001185540100001 ()2-s2.0-85186903501 (Scopus ID)
Available from: 2024-05-15 Created: 2024-05-15 Last updated: 2024-05-15Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Measurement of the t¯t¯ cross section and its ratio to the Z production cross section using pp collisions at √s=13.6 TeV with the ATLAS detector. Physics Letters B, 848, Article ID 138376.
Open this publication in new window or tab >>Measurement of the t¯t¯ cross section and its ratio to the Z production cross section using pp collisions at √s=13.6 TeV with the ATLAS detector
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2024 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 848, article id 138376Article in journal (Refereed) Published
Abstract [en]

The inclusive top-quark-pair production cross section 𝜎𝑡𝑡̄ and its ratio to the 𝑍-boson production cross section have been measured in proton–proton collisions at √𝑠 = 13.6 TeV, using 29 fb−1 of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and 𝑏-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be 𝜎𝑡𝑡̄ = 850± 3(stat.) ± 18(syst.) ± 20(lumi.) pb. The ratio of the 𝑡𝑡̄ and the 𝑍-boson production cross sections is also measured, where the 𝑍-boson contribution is determined for inclusive 𝑒+𝑒 and 𝜇+𝜇 events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the 𝑡𝑡̄ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, 𝑅𝑡𝑡̄∕𝑍 = 1.145 ± 0.003(stat.) ± 0.021(syst.)±0.002(lumi.) is consistent with the Standard Model prediction using the PDF4LHC21 PDF set.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-225966 (URN)10.1016/j.physletb.2023.138376 (DOI)001136441300001 ()
Available from: 2024-01-30 Created: 2024-01-30 Last updated: 2024-01-30Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Performance and calibration of quark/gluon-jet taggers using 140 fb-1 of pp collisions at √s=13 TeV with the ATLAS detector. Chinese Physics C, 48(2), Article ID 023001.
Open this publication in new window or tab >>Performance and calibration of quark/gluon-jet taggers using 140 fb-1 of pp collisions at √s=13 TeV with the ATLAS detector
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2024 (English)In: Chinese Physics C, ISSN 1674-1137, E-ISSN 2058-6132, Vol. 48, no 2, article id 023001Article in journal (Refereed) Published
Abstract [en]

The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using √𝑠=13 TeV proton–proton collision data with an integrated luminosity of 140 fb−1 collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.

Keywords
ATLAS, JET, QUARK, GLUON, TAGGING
National Category
Subatomic Physics Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:su:diva-228693 (URN)10.1088/1674-1137/acf701 (DOI)001187976400001 ()2-s2.0-85185169176 (Scopus ID)
Available from: 2024-05-02 Created: 2024-05-02 Last updated: 2024-05-02Bibliographically approved
Aad, G., Andrean, S. Y., Backman, F., Barranco Navarro, L., Bohm, C., Clément, C., . . . Zwalinski, L. (2024). Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a Z boson in the ℓ+ℓ−𝑡𝑡¯ and 𝜈𝜈¯𝑏𝑏¯ final states using 140 fb−1 of data collected with the ATLAS detector. Journal of High Energy Physics (JHEP), 2024(2), Article ID 197.
Open this publication in new window or tab >>Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a Z boson in the ℓ+𝑡𝑡¯ and 𝜈𝜈¯𝑏𝑏¯ final states using 140 fb1 of data collected 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 2, article id 197Article in journal (Refereed) Published
Abstract [en]

A search for a heavy CP-odd Higgs boson, A, decaying into a Z boson and a heavy CP-even Higgs boson, H, is presented. It uses the full LHC Run 2 dataset of pp collisions at √𝑠 = 13 TeV collected with the ATLAS detector, corresponding to an integrated luminosity of 140 fb−1. The search for AZH is performed in the ℓ+ and final states and surpasses the reach of previous searches in different final states in the region with mH > 350 GeV and mA > 800 GeV. No significant deviation from the Standard Model expectation is found. Upper limits are placed on the production cross-section times the decay branching ratios. Limits with less model dependence are also presented as functions of the reconstructed and distributions in the ℓ+ and channels, respectively. In addition, the results are interpreted in the context of two-Higgs-doublet models.

Keywords
Hadron-Hadron Scattering
National Category
Subatomic Physics
Identifiers
urn:nbn:se:su:diva-228695 (URN)10.1007/JHEP02(2024)197 (DOI)001185484300001 ()2-s2.0-85190986940 (Scopus ID)
Available from: 2024-05-02 Created: 2024-05-02 Last updated: 2024-05-02Bibliographically approved
Organisations
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7818-2324

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