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    557 research outputs found

    Author Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery

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    Crossref
    Archivio della Ricerca - Università di Pisa

    Search for same-charge top-quark pair production in pp collisions at √s = 13 TeV with the ATLAS detector

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    A search for the production of top-quark pairs with the same electric charge (tt or t¯t¯) is presented. The analysis uses proton-proton collision data at √ s = 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1 . Events with two same-charge leptons and at least two b-tagged jets are selected. Neural networks are employed to define two selections sensitive to additional couplings beyond the Standard Model that would enhance the production rate of same-sign top-quark pairs. No significant signal is observed, leading to an upper limit on the total production cross-section of same-sign top-quark pairs of 1.6 fb at 95% confidence level. Corresponding limits on the three Wilson coefficients associated with the O (1) tu , O (1) Qu, and O (8) Qu operators in the Standard Model Effective Field Theory framework are derived
    Archives ouvertes de Paris-Saclay
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    HAL Université de Toulouse, et Toulouse INP
    AIR Universita degli studi di Milano
    eScholarship - University of California
    Archivio della Ricerca - Università di Roma 3
    Enlighten
    Queen Mary Research Online
    ART
    White Rose Research Online

    Search for heavy, long-lived, charged particles with large ionisation energy loss in pp collisions at s s \sqrt{s} = 13 TeV using the ATLAS experiment and the full Run 2 dataset

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    Abstract This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb −1 of proton–proton collisions at s s \sqrt{s} = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to O O \mathcal{O} (1) ns with a mass, measured using the Bethe–Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    Directory of Open Access Journals
    Unisa Institutional Repository
    Archivio istituzionale della ricerca - Università di Genova
    White Rose Research Online
    Archives ouvertes de Paris-Saclay
    Bergen Open Research Archive (Univ. of Bergen)
    AIR Universita degli studi di Milano
    Archivio Istituzionale della Ricerca - Università degli Studi di Pavia
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Archive ouverte de Sorbonne Université
    HAL
    Hal - Université Grenoble Alpes
    HAL AMU
    HAL Clermont Université
    HAL Université de Savoie
    Enlighten
    Queen Mary Research Online
    ART
    HAL-CEA
    İstanbul Üniversitesi Açık Erişim Sistemi
    Archivio della ricerca - Università degli studi di Napoli "Parthenope"
    HAL-IN2P3
    HAL Université de Toulouse, et Toulouse INP
    Archivio della Ricerca - Università di Roma 3

    Measurements of the Higgs boson inclusive and differential fiducial cross-sections in the diphoton decay channel with pppp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

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    A measurement of inclusive and differential fiducial cross-sections for the production of the Higgs boson decaying into two photons is performed using 139 fb−1139~\text{fb}^{-1} of proton--proton collision data recorded at s=13\sqrt{s} = 13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio, in a fiducial region closely matching the experimental selection, is measured to be 67±667\pm 6 fb, which is in agreement with the state-of-the-art Standard Model prediction of 64±464\pm 4 fb. Extrapolating this result to the full phase space and correcting for the branching ratio, the total cross-section for Higgs boson production is estimated to be 58±658\pm 6 pb. In addition, the cross-sections in four fiducial regions sensitive to various Higgs boson production modes and differential cross-sections as a function of either one or two of several observables are measured. All the measurements are found to be in agreement with the Standard Model predictions. The measured transverse momentum distribution of the Higgs boson is used as an indirect probe of the Yukawa coupling of the Higgs boson to the bottom and charm quarks. In addition, five differential cross-section measurements are used to constrain anomalous Higgs boson couplings to vector bosons in the Standard Model effective field theory framework.Comment: 96 pages in total, author list starting page 80, 38 figures, 7 tables, published by JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2019-13
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    The University of Arizona
    Enlighten
    Queen Mary Research Online
    ART
    Archivio istituzionale della ricerca - Università di Genova
    University of British Columbia: cIRcle - UBC's Information Repository
    White Rose Research Online
    Archive ouverte UNIGE
    arXiv.org e-Print Archive
    Archivio della ricerca - Università degli studi di Napoli "Parthenope"
    Crossref
    AIR Universita degli studi di Milano
    Archivio Istituzionale della Ricerca - Università degli Studi di Pavia
    Archivio della ricerca - Fondazione Bruno Kessler
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Lancaster E-Prints
    Archivio della ricerca- Università di Roma La Sapienza

    Measurement of the energy asymmetry in ttˉjt\bar{t}j production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework

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    A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using 139 fb−1\mathrm{fb}^{-1} of data collected by the ATLAS detector at the Large Hadron Collider during pppp collisions at s=13\sqrt{s}=13 TeV. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic ttˉt\bar{t} decay channel, and the hadronically decaying top quark must have transverse momentum above 350350 GeV. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be −0.043±0.020-0.043\pm0.020, in agreement with the SM prediction of −0.037±0.003-0.037\pm0.003. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.Comment: 52 pages in total, author list starting page 37, 10 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2019-2
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    EDP Sciences OAI-PMH repository (1.2.0)
    The University of Arizona
    Enlighten
    Queen Mary Research Online
    NORA - Norwegian Open Research Archives
    ART
    Archivio istituzionale della ricerca - Università di Genova
    University of British Columbia: cIRcle - UBC's Information Repository
    White Rose Research Online
    arXiv.org e-Print Archive
    Bergen Open Research Archive (Univ. of Bergen)
    AIR Universita degli studi di Milano
    Archivio Istituzionale della Ricerca - Università degli Studi di Pavia
    eScholarship - University of California
    Archivio della Ricerca - Università di Roma 3
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Lancaster E-Prints
    Archivio della ricerca- Università di Roma La Sapienza

    Observation of quantum entanglement in top-quark pairs using the ATLAS detector

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    Entanglement is a key feature of quantum mechanics, with applications in fields such as metrology, cryptography, quantum information, and quantum computation. It has been observed in a wide variety of systems and length scales, ranging from the microscopic to the macroscopic. However, entanglement remains largely unexplored at the highest accessible energy scales. Here we report the highest-energy observation of entanglement, in top−-antitop quark events produced at the Large Hadron Collider, using a proton−-proton collision dataset with a center-of-mass energy of s=13\sqrt{s}=13 TeV and an integrated luminosity of 140 fb−1^{-1} recorded with the ATLAS experiment. Spin entanglement is detected from the measurement of a single observable DD, inferred from the angle between the charged leptons in their parent top- and antitop-quark rest frames. The observable is measured in a narrow interval around the top−-antitop quark production threshold, where the entanglement detection is expected to be significant. It is reported in a fiducial phase space defined with stable particles to minimize the uncertainties that stem from limitations of the Monte Carlo event generators and the parton shower model in modeling top-quark pair production. The entanglement marker is measured to be D=−0.537±0.002 (stat.)±0.019 (syst.)D=-0.537 \pm 0.002~\text{(stat.)} \pm 0.019~\text{(syst.)} for 340<mttˉ<380340 < m_{t\bar{t}} < 380 GeV. The observed result is more than five standard deviations from a scenario without entanglement and constitutes the first observation of entanglement in a pair of quarks and the highest-energy observation of entanglement so far.49 pages in total, author list starting page 32, 4 figures, 2 tables, published as Nature 633 (2024) 542. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2021-2
    arXiv.org e-Print Archive
    University of Liverpool Repository
    Hong Kong University of Science and Technology Institutional Repository
    Queen Mary Research Online
    University of Melbourne Institutional Repository

    Search for Higgs boson pair production in association with a vector boson in pp collisions at s=13 TeV\sqrt{s}=13\,\text {TeV} s = 13 TeV with the ATLAS detector

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    Abstract This paper reports a search for Higgs boson pair (hh) production in association with a vector boson ( W  or  ZW\; {\text {o}r}\; Z W o r Z ) using 139 fb −1^{-1} - 1 of proton–proton collision data at s=13 TeV\sqrt{s}=13\,\text {TeV} s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed in final states in which the vector boson decays leptonically ( W→ℓν, Z→ℓℓ,ννW\rightarrow \ell \nu ,\, Z\rightarrow \ell \ell ,\nu \nu W → ℓ ν , Z → ℓ ℓ , ν ν with ℓ=e,μ\ell =e, \mu ℓ = e , μ ) and the Higgs bosons each decay into a pair of b-quarks. It targets Vhh signals from both non-resonant hh production, present in the Standard Model (SM), and resonant hh production, as predicted in some SM extensions. A 95% confidence-level upper limit of 183 (87) times the SM cross-section is observed (expected) for non-resonant Vhh production when assuming the kinematics are as expected in the SM. Constraints are also placed on Higgs boson coupling modifiers. For the resonant search, upper limits on the production cross-sections are derived for two specific models: one is the production of a vector boson along with a neutral heavy scalar resonance H, in the mass range 260–1000 GeV, that decays into hh, and the other is the production of a heavier neutral pseudoscalar resonance A that decays into a Z boson and H boson, where the A boson mass is 360–800 GeV and the H boson mass is 260–400 GeV. Constraints are also derived in the parameter space of two-Higgs-doublet models
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    AIR Universita degli studi di Milano
    EDP Sciences OAI-PMH repository (1.2.0)
    Directory of Open Access Journals
    eScholarship - University of California
    Archivio della Ricerca - Università di Roma 3
    DESY
    Enlighten
    Queen Mary Research Online
    ART
    White Rose Research Online

    Search for heavy, long-lived, charged particles with large ionisation energy loss in pp collisions at root s=13 TeV using the ATLAS experiment and the full Run 2 dataset

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    This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb−1 of proton–proton collisions at s = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to O (1) ns with a mass, measured using the Bethe–Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime. [Figure not available: see fulltext.
    Archivio della Ricerca - Università degli Studi di Siena
    Archivio istituzionale della ricerca - Università degli Studi di Udine
    Archivio della Ricerca - Università di Pisa
    ePubs: the open archive for STFC research publications

    Configuration, performance, and commissioning of the ATLAS b-jet triggers for the 2022 and 2023 LHC data-taking periods

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    In 2022 and 2023, the Large Hadron Collider produced approximately two billion hadronic interactions each second from bunches of protons that collide at a rate of 40 MHz. The ATLAS trigger system is used to reduce this rate to a few kHz for recording. Selections based on hadronic jets, their energy, and event topology reduce the rate to O (10) kHz while maintaining high efficiencies for important signatures resulting in b-quarks, but to reach the desired recording rate of hundreds of Hz, additional real-time selections based on the identification of jets containing b-hadrons (b-jets) are employed to achieve low thresholds on the jet transverse momentum at the High-Level Trigger. The configuration, commissioning, and performance of the real-time ATLAS b-jet identification algorithms for the early LHC Run 3 collision data are presented. These recent developments provide substantial gains in signal efficiency for critical signatures; for the Standard Model production of Higgs boson pairs, a 50% improvement in selection efficiency is observed in final states with four b-quarks or two b-quarks and two hadronically decaying τ-leptons
    Archives ouvertes de Paris-Saclay
    AIR Universita degli studi di Milano
    Enlighten
    Queen Mary Research Online
    ART
    White Rose Research Online
    Portail HAL-PSL

    Search for light long-lived neutral particles that decay to collimated pairs of leptons or light hadrons in pp collisions at s√ = 13 TeV with the ATLAS detector

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    A search for light long-lived neutral particles with masses in the O(MeV–GeV) range is presented. The analysis targets the production of long-lived dark photons in the decay of a Higgs boson produced via gluon–gluon fusion or in association with a W boson. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are selected in 139 fb−1 of s√ = 13 TeV pp collision data collected by the ATLAS detector at the LHC. Background estimates for contributions from Standard Model processes and instrumental effects are extracted from data. The observed event yields are consistent with the expected background. Exclusion limits are reported on the production cross-section times branching fraction as a function of the mean proper decay length cτ of the dark photon, or as a function of the dark-photon mass and kinetic mixing parameter that quantifies the coupling between the Standard Model and potential hidden (dark) sectors. A Higgs boson branching fraction above 1% is excluded at 95% CL for a Higgs boson decaying into two dark photons for dark-photon mean proper decay lengths between 10 mm and 250 mm and dark photons with masses between 0.4 GeV and 2 GeV
    University of Liverpool Repository
    Pontificia Universidad Católica de Chile: Repositorio UC
    Hal - Université Grenoble Alpes
    HAL AMU
    Directory of Open Access Journals
    HAL Clermont Université
    Unisa Institutional Repository
    HAL Université de Savoie
    Enlighten
    Queen Mary Research Online
    ART
    Archivio istituzionale della ricerca - Università di Genova
    HAL-CEA
    White Rose Research Online
    Archives ouvertes de Paris-Saclay
    Archivio della ricerca - Università degli studi di Napoli &quot;Parthenope&quot;
    HAL-IN2P3
    AIR Universita degli studi di Milano
    Archivio Istituzionale della Ricerca - Università degli Studi di Pavia
    eScholarship - University of California
    Archivio della Ricerca - Università di Roma 3
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    HAL-OBSPM
    HAL
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