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Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). Measurement of muon pairs produced via γγ scattering in nonultraperipheral Pb + Pb collisions at √sNN = 5.02 TeV with the ATLAS detector. Physical Review C: Covering Nuclear Physics, 107(5), Article ID 054907.
Open this publication in new window or tab >>Measurement of muon pairs produced via γγ scattering in nonultraperipheral Pb + Pb collisions at √sNN = 5.02 TeV with the ATLAS detector
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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 054907Article in journal (Refereed) Published
Abstract [en]

Results of a measurement of dimuon photoproduction in nonultraperipheral Pb + Pb collisions at √sNN = 5.02 TeV are presented. Themeasurement uses ATLAS data from the 2015 and 2018 Pb + Pb data-taking periods at the LHC with an integrated luminosity of 1.94 nb.1. The γγ → μ+ μ- pairs are identified via selections on pair momentum asymmetry and acoplanarity. Differential cross sections for dimuon production are measured in different centrality, average muon momentum, and pair rapidity intervals as functions of acoplanarity and k⊥, the transverse momentum kick of one muon relative to the other. Measurements are also made as a function of the rapidity separation of the muons and the angle of the muon pair relative to the second-order event plane to test whether magnetic fields generated in the quark-gluon plasma affect the measured muons. A prior observation of a centrality-dependent broadening of the acoplanarity distribution is confirmed. Furthermore, the improved precision of the measurement reveals a depletion in the number of pairs having small acoplanarity or k⊥ values in more central collisions. The acoplanarity distributions in a given centrality interval are observed to vary with the mean pT of the muons in the pair, but the k⊥ distributions do not. Comparisons with recent theoretical predictions are made. The predicted trends associated with effects of magnetic fields on the dimuons are not observed.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-335313 (URN)10.1103/PhysRevC.107.054907 (DOI)2-s2.0-85166613350 (Scopus ID)
Note

QC 20230905

Available from: 2023-09-05 Created: 2023-09-05 Last updated: 2023-09-05Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2023). Measurement of the CP properties of Higgs boson interactions with τ-leptons with the ATLAS detector. European Physical Journal C, 83(7), Article ID 563.
Open this publication in new window or tab >>Measurement of the CP properties of Higgs boson interactions with τ-leptons with the ATLAS detector
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2023 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 7, article id 563Article in journal (Refereed) Published
Abstract [en]

A study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and tau -leptons is presented. The study is based on a measurement of CP-sensitive angular observables defined by the visible decay products of t -leptons produced in Higgs boson decays. The analysis uses 139 fb(-1) of proton-proton collision data recorded at a centre-of-mass energy of root s = 13 TeV with the ATLAS detector at the Large Hadron Collider. Contributions from CP-violating interactions between the Higgs boson and t -leptons are described by a single mixing angle parameter phi(tau) in the generalised Yukawa interaction. Without constraining the H -> tau tau signal strength to its expected value under the Standard Model hypothesis, the mixing angle ft is measured to be 9 degrees +/- 16 degrees, with an expected value of 0 degrees +/- 28 degrees at the 68% confidence level. The pure CPodd hypothesis is disfavoured at a level of 3.4 standard deviations. The results are compatible with the predictions for the Higgs boson in the Standard Model.

Place, publisher, year, edition, pages
Springer, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-339390 (URN)10.1140/epjc/s10052-023-11583-y (DOI)001062395800002 ()
Note

QC 20231108

Available from: 2023-11-08 Created: 2023-11-08 Last updated: 2023-11-08Bibliographically approved
Jackson, P., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). Measurement of the inclusive Formula Presented production cross section in the lepton+jets channel in pp collisions at Formula Presented with the ATLAS detector using support vector machines. Physical Review D: covering particles, fields, gravitation, and cosmology, 108(3), Article ID 032014.
Open this publication in new window or tab >>Measurement of the inclusive Formula Presented production cross section in the lepton+jets channel in pp collisions at Formula Presented with the ATLAS detector using support vector machines
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2023 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 108, no 3, article id 032014Article in journal (Refereed) Published
Abstract [en]

A measurement of the top quark pair-production cross section in the lepton + jets decay channel is presented. It is based on 4.6 fb - 1 of s = 7 TeV p p collision data collected during 2011 by the ATLAS experiment at the CERN Large Hadron Collider. A three-class, multidimensional event classifier based on support vector machines is used to differentiate t t ¯ events from backgrounds. The t t ¯ production cross section is found to be σ t t ¯ = 168.5 ± 0.7 ( stat ) - 5.9 + 6.2 ( syst ) - 3.2 + 3.4 ( lumi ) pb . The result is consistent with the Standard Model prediction based on QCD calculations at next-to-next-to-leading order.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-338878 (URN)10.1103/PhysRevD.108.032014 (DOI)001063420300001 ()2-s2.0-85173785320 (Scopus ID)
Note

QC 20231031

Available from: 2023-10-31 Created: 2023-10-31 Last updated: 2023-11-15Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). Measurement of the top-quark mass using a leptonic invariant mass in pp collisions at √s = 13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), 2023(6), Article ID 19.
Open this publication in new window or tab >>Measurement of the top-quark mass using a leptonic invariant mass 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 19Article in journal (Refereed) Published
Abstract [en]

A measurement of the top-quark mass (mt) in the tt¯ → lepton + jets channel is presented, with an experimental technique which exploits semileptonic decays of b-hadrons produced in the top-quark decay chain. The distribution of the invariant mass mℓμ of the lepton, ℓ (with ℓ = e, μ), from the W-boson decay and the muon, μ, originating from the b-hadron decay is reconstructed, and a binned-template profile likelihood fit is performed to extract mt. The measurement is based on data corresponding to an integrated luminosity of 36.1 fb−1 of s = 13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. The measured value of the top-quark mass is mt = 174.41 ± 0.39 (stat.) ± 0.66 (syst.) ± 0.25 (recoil) GeV, where the third uncertainty arises from changing the Pythia8 parton shower gluon-recoil scheme, used in top-quark decays, to a recently developed setup. [Figure not available: see fulltext.].

Place, publisher, year, edition, pages
Springer Science and Business Media Deutschland GmbH, 2023
Keywords
Hadron-Hadron Scattering, Top Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-331635 (URN)10.1007/JHEP06(2023)019 (DOI)001035480600001 ()2-s2.0-85161860997 (Scopus ID)
Note

QC 20230714

Available from: 2023-07-14 Created: 2023-07-14 Last updated: 2023-09-22Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2023). Measurements of differential cross sections of Higgs boson production through gluon fusion in the H → WW *→ eνμν final state at √s=13 TeV with the ATLAS detector. European Physical Journal C, 83(9), Article ID 774.
Open this publication in new window or tab >>Measurements of differential cross sections of Higgs boson production through gluon fusion in the H → WW *→ eνμν final state at √s=13 TeV with the ATLAS detector
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2023 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 9, article id 774Article in journal (Refereed) Published
Abstract [en]

Higgs boson production via gluon-gluon fusion is measured in the WW *-> e nu mu nu decay channel. The dataset utilized corresponds to an integrated luminosity of 139 fb(-1) collected by the ATLAS detector from root s = 13TeV proton-proton collisions delivered by the Large Hadron Collider between 2015 and 2018. Differential cross sections are measured in a fiducial phase space restricted to the production of at most one additional jet. The results are consistent with Standard Model expectations, derived using different Monte Carlo generators.

Place, publisher, year, edition, pages
Springer, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-339393 (URN)10.1140/epjc/s10052-023-11873-5 (DOI)001062396000001 ()
Note

QC 20231108

Available from: 2023-11-08 Created: 2023-11-08 Last updated: 2023-11-08Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). Model-independent search for the presence of new physics in events including H → γγ with s√ = 13 TeV pp data recorded by the ATLAS detector at the LHC. Journal of High Energy Physics (JHEP) (7), Article ID 176.
Open this publication in new window or tab >>Model-independent search for the presence of new physics in events including H → γγ with s√ = 13 TeV pp data recorded by the ATLAS detector at the LHC
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2023 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 7, article id 176Article in journal (Refereed) Published
Abstract [en]

A model-independent search for new physics leading to final states containing a Higgs boson, with a mass of 125.09 GeV, decaying to a pair of photons is performed with 139 fb(-1) of p root s = 13TeV pp collision data recorded by the ATLAS detector at the Large Hadron Collider at CERN. This search examines 22 final states categorized by the objects that are produced in association with the Higgs boson. These objects include isolated electrons or muons, hadronically decaying iota -leptons, additional photons, missing transverse momentum, and hadronic jets, as well as jets that are tagged as containing a b-hadron. No significant excesses above Standard Model expectations are observed and limits on the production cross section at 95% confidence level are set. Detector efficiencies are reported for all 22 signal regions, which can be used to convert detector-level cross-section limits reported in this paper to particle-level cross-section constraints.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
Hadron-Hadron Scattering, Higgs Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-338240 (URN)10.1007/JHEP07(2023)176 (DOI)001062072300001 ()
Note

QC 20231017

Available from: 2023-10-17 Created: 2023-10-17 Last updated: 2023-10-17Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). New techniques for jet calibration with the ATLAS detector. European Physical Journal C, 83(8), Article ID 761.
Open this publication in new window or tab >>New techniques for jet calibration with the ATLAS detector
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2023 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 8, article id 761Article in journal (Refereed) Published
Abstract [en]

A determination of the jet energy scale is presented using proton-proton collision data with a centre-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 140 fb(-1) collected using the ATLAS detector at the LHC. Jets are reconstructed using the ATLAS particle-flow method that combines charged-particle tracks and topo-clusters formed from energy deposits in the calorimeter cells. The anti-kt jet algorithm with radius parameter R = 0.4 is used to define the jet. Novel jet energy scale calibration strategies developed for the LHC Run 2 are reported that lay the foundation for the jet calibration in Run 3. Jets are calibrated with a series of simulation-based corrections, including state-of-the-art techniques in jet calibration such as machine learning methods and novel in situ calibrations to achieve better performance than the baseline calibration derived using up to 81 fb(-1) of Run 2 data. The performance of these new techniques is then examined in the in situ measurements by exploiting the transverse momentum balance between a jet and a reference object. The b-quark jet energy scale using particle flow jets is measured for the first time with around 1% precision using gamma+jet events.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-339652 (URN)10.1140/epjc/s10052-023-11837-9 (DOI)001062421500007 ()2-s2.0-85179172081 (Scopus ID)
Note

QC 20231115

Available from: 2023-11-15 Created: 2023-11-15 Last updated: 2024-07-11Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J., . . . et al., . (2023). Observation of electroweak production of two jets and a Z-boson pair. Nature Physics, 19(2)
Open this publication in new window or tab >>Observation of electroweak production of two jets and a Z-boson pair
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2023 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 19, no 2Article in journal (Refereed) Published
Abstract [en]

Electroweak symmetry breaking explains the origin of the masses of elementary particles through their interactions with the Higgs field. Besides the measurements of the Higgs boson properties, the study of the scattering of massive vector bosons with spin one allows the nature of electroweak symmetry breaking to be probed. Among all processes related to vector-boson scattering, the electroweak production of two jets and a Z-boson pair is a rare and important one. Here we report the observation of this process from proton-proton collision data corresponding to an integrated luminosity of 139 fb(-1) recorded at a centre-of-mass energy of 13 TeV with the ATLAS detector at the Large Hadron Collider. We consider two different final states originating from the decays of the Z-boson pair - one containing four charged leptons and the other containing two charged leptons and two neutrinos. The hypothesis of no electroweak production is rejected with a statistical significance of 5.7 sigma, and the measured cross-section for electroweak production is consistent with the standard model prediction. In addition, we report cross-sections for inclusive production of a Z-boson pair and two jets for the two final states.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Subatomic Physics Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:kth:diva-336056 (URN)10.1038/s41567-022-01757-y (DOI)001043154600001 ()2-s2.0-85158900669 (Scopus ID)
Note

QC 20230911

Available from: 2023-09-11 Created: 2023-09-11 Last updated: 2023-11-16Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2023). Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at s=13 TeV. Physics Letters B, 842, Article ID 137379.
Open this publication in new window or tab >>Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at s=13 TeV
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2023 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 842, article id 137379Article in journal (Refereed) Published
Abstract [en]

This letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly sup-pressed in the Standard Model, in events with a photon and a top quark with the ATLAS detector. The analysis uses data collected in pp collisions at & RADIC;s =13 TeV during Run 2 of the LHC, corresponding to an integrated luminosity of 139 fb-1. Both FCNC top-quark production and decay are considered. The final state consists of a charged lepton, missing transverse momentum, a b-tagged jet, one high-momentum photon and possibly additional jets. A multiclass deep neural network is used to classify events either as signal in one of the two categories, FCNC production or decay, or as background. No signifiThis letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly suppressed in the Standard Model, in events with a photon and a top quark with the ATLAS detector. The analysis uses data collected in pp collisions at s=13 TeV during Run 2 of the LHC, corresponding to an integrated luminosity of 139 fb−1. Both FCNC top-quark production and decay are considered. The final state consists of a charged lepton, missing transverse momentum, a b-tagged jet, one high-momentum photon and possibly additional jets. A multiclass deep neural network is used to classify events either as signal in one of the two categories, FCNC production or decay, or as background. No significant excess of events over the background prediction is observed and 95% CL upper limits are placed on the strength of left- and right-handed FCNC interactions. The 95% CL bounds on the branching fractions for the FCNC top-quark decays, estimated (expected) from both top-quark production and decay, are B(t→uγ)<0.85(0.88−0.25+0.37)×10−5 and B(t→cγ)<4.2(3.40−0.95+1.35)×10−5 for a left-handed tqγ coupling, and B(t→uγ)<1.2(1.20−0.33+0.50)×10−5 and B(t→cγ)<4.5(3.70−1.03+1.47)×10−5 for a right-handed coupling.cant ex-cess of events over the background prediction is observed and 95% CL upper limits are placed on the strength of left-and right-handed FCNC interactions. The 95% CL bounds on the branching fractions for the FCNC top-quark decays, estimated (expected) from both top-quark production and decay, are B(tγ) < 0.85 (0.88+0.37 -0.25) x 10-5 and B(tγ) < 4.2 (3.40+1.35-0.95) x 10-5 for a left-handed tqγ, and B(tγ) < 1.2 (1.20+0.50 -0.33) x10-5 and B(tγ) < 4.5 (3.70+1.47 -1.03) x10-5 for a right-handed coupling.

Place, publisher, year, edition, pages
ELSEVIER, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-337011 (URN)10.1016/j.physletb.2022.137379 (DOI)001023760300001 ()2-s2.0-85146929561 (Scopus ID)
Note

QC 20230922

Available from: 2023-09-22 Created: 2023-09-22 Last updated: 2023-09-22Bibliographically approved
Aad, G., Lund-Jensen, B., Ohm, C., Ripellino, G., Sidebo, P. E., Strandberg, J. & Zwalinski, L. (2023). Search for supersymmetry in final states with missing transverse momentum and three or more b-jets in 139 fb-1 of proton-proton collisions at √s=13 TeV with the ATLAS detector. European Physical Journal C, 83(7), Article ID 561.
Open this publication in new window or tab >>Search for supersymmetry in final states with missing transverse momentum and three or more b-jets in 139 fb-1 of proton-proton collisions at √s=13 TeV with the ATLAS detector
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2023 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 7, article id 561Article in journal (Refereed) Published
Abstract [en]

A search for supersymmetry involving the pair production of gluinos decaying via off-shell third-generation squarks into the lightest neutralino ((chi) over tilde (0)(1)) is reported. It exploits LHC proton-proton collision data at a centre-ofmass energy root s = 13 TeV with an integrated luminosity of 139 fb(-1) collected with the ATLAS detector from 2015 to 2018. The search uses events containing large missing transverse momentum, up to one electron or muon, and several energetic jets, at least three of which must be identified as containing b-hadrons. Both a simple kinematic event selection and an event selection based upon a deep neural network are used. No significant excess above the predicted background is found. In simplified models involving the pair production of gluinos that decay via off-shell top (bottom) squarks, gluino masses less than 2.44 TeV (2.35 TeV) are excluded at 95% CL for a massless (chi) over tilde (0)(1). Limits are also set on the gluino mass in models with variable branching ratios for gluino decays to b (b) over bar (chi) over tilde (0)(1), t (t) over bar (chi) over tilde (0)(1) and t (b) over bar (chi) over tilde (-)(iota) / (t) over barb (chi) over tilde (0)(1).

Place, publisher, year, edition, pages
Springer, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-339389 (URN)10.1140/epjc/s10052-023-11543-6 (DOI)001062395800001 ()
Note

QC 20231108

Available from: 2023-11-08 Created: 2023-11-08 Last updated: 2023-11-08Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-0299-8236

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