12 research outputs found

    Study of Z → llγ decays at √s = 8 TeV with the ATLAS detector

    Get PDF
    This paper presents a study of Z → llγ decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton–proton data sample corresponding to an integrated luminosity of 20.2 fb−1 collected at a centre-ofmass energy √s = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with stateof-the-art predictions for final-state QED radiation. First measurements of Z → llγ γ decays are also reported

    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

    Get PDF
    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 (0.30+0.13−0.09) is observed (expected) at 95% confidence level

    Search for long-lived neutral particles in pp collisions at s√=13 TeV that decay into displaced hadronic jets in the ATLAS calorimeter

    Get PDF
    This paper describes a search for pairs of neutral, long-lived particles decaying in the ATLAS calorimeter. Long-lived particles occur in many extensions to the Standard Model and may elude searches for new promptly decaying particles. The analysis considers neutral, long-lived scalars with masses between 5 and 400 GeV, produced from decays of heavy bosons with masses between 125 and 1000 GeV, where the long-lived scalars decay into Standard Model fermions. The analysis uses either 10.8 fb−1 or 33.0 fb−1 of data (depending on the trigger) recorded in 2016 at the LHC with the ATLAS detector in proton–proton collisions at a centre-of-mass energy of 13 TeV. No significant excess is observed, and limits are reported on the production cross section times branching ratio as a function of the proper decay length of the long-lived particles

    Deep generative models for fast photon shower simulation in ATLAS

    Get PDF
    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 geant4. 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

    Search for doubly charged Higgs boson production in multi-lepton final states using 139 fb−1 of proton–proton collisions at s√ = 13 TeV with the ATLAS detector

    Get PDF
    A search for pair production of doubly charged Higgs bosons (H±± ), each decaying into a pair of prompt, isolated, and highly energetic leptons with the same electric charge, is presented. The search uses a proton–proton collision data sample at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 139 fb−1 recorded by the ATLAS detector during Run 2 of the Large Hadron Collider (LHC). This analysis focuses on same-charge leptonic decays, H±±→ℓ±ℓ′± where ℓ,ℓ′=e,μ,τ, in two-, three-, and four-lepton channels, but only considers final states which include electrons or muons. No evidence of a signal is observed. Corresponding upper limits on the production cross-section of a doubly charged Higgs boson are derived, as a function of its mass m(H±±), at 95% confidence level. Assuming that the branching ratios to each of the possible leptonic final states are equal, B(H±±→e±e±)=B(H±±→e±μ±)=B(H±±→μ±μ±)=B(H±±→e±τ±)=B(H±±→μ±τ±)=B(H±±→τ±τ±)=1/6, the observed (expected) lower limit on the mass of a doubly charged Higgs boson is 1080 GeV (1065 GeV) within the left-right symmetric type-II seesaw model, which is the strongest limit to date produced by the ATLAS Collaboration. Additionally, this paper provides the first direct test of the Zee–Babu neutrino mass model at the LHC, yielding an observed (expected) lower limit of m(H±±) = 900 GeV (880 GeV)

    Endocytic Pathways Downregulate the L1-type Cell Adhesion Molecule Neuroglian to Promote Dendrite Pruning in Drosophila

    No full text
    10.1016/j.devcel.2014.06.014Developmental Cell304463-47

    Regional differences in percutaneous coronary intervention outcomes in STEMI patients with diabetes: The Asia-Pacific evaluation of cardiovascular therapies (ASPECT) collaboration

    No full text
    Background: Diabetes is associated with poorer outcomes and increased complication rates in STEMI patients undergoing percutaneous coronary intervention (PCI). Data are notably lacking in the Asia-Pacific region. We report the overall association of Diabetes with clinical characteristics and outcomes in STEMI patients undergoing PCI across the Asia-Pacific, with a particular focus on regional differences. Methodology: The Asia Pacific Evaluation of Cardiovascular Therapies (ASPECT) collaboration consists of data from various PCI registries across Australia, Hong Kong, Singapore, Malaysia, Indonesia and Vietnam. Clinical characteristics, lesion characteristics, and outcomes were provided for STEMI patients. Key outcomes included 30-day overall mortality and major adverse cardiovascular events (MACE). Results: A total of 12,144 STEMI patients (mean(SD) age 59.3(12.3)) were included, of which 3912 (32.2%) had diabetes. Patients with diabetes were likely to have a higher baseline risk profile, poorer clinical presentation, and more complex lesion patterns (all p < 0.05). Across all regions, patients with diabetes had a higher rate of 30- day mortality and MACE (all p < 0.05). After multivariable adjustment, diabetes was significantly associated with both increased 30-day mortality (9.6%vs 5.5%, OR 1.79 [95% CI 1.40–2.30]) and MACE (13.3% vs 8.6%, R 1.73 [1.44–2.08]). The association between diabetes and 30-day MACE varied by region (pinteraction = 0.041), with the association (OR) ranging from 1.34 [1.08–1.67] in Malaysia, to 2.39 [1.66–3.45] in Singapore. Conclusions: Diabetes portends poorer clinical outcomes in STEMI patients undergoing PCI in the Asia-Pacific with regional variations noted. The development of effective preventative measures and interventional strategies targetted at this high-risk group is crucial.Mark Y.Z. Wong, Jonathan J.L. Yap, Hui Jun Chih, Bryan P.Y. Yan, Alan Y.Y. Fong, John F. Beltrame, Ika Prasetya Wijaya, Hoai T.T. Nguyen, Angela L. Brennan, Christopher M. Reid, Khung Keong Ye
    corecore