1,574 research outputs found

    Measurement of the Z boson invisible width at s=13 TeV with the ATLAS detector

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    A measurement of the invisible width of the Z boson using events with jets and missing transverse momentum is presented using 37 fb−1 of 13 TeV proton–proton data collected by the ATLAS detector in 2015 and 2016. The ratio of Z→inv to Z→ll events, where inv refers to non-detected particles and l is either an electron or a muon, is measured and corrected for detector effects. Events with at least one energetic central jet with pT≥110 GeV are selected for both the Z→inv and Z→ll final states to obtain a similar phase space in the ratio. The invisible width is measured to be 506±2(stat.)±12(syst.) MeV and is the single most precise recoil-based measurement. The result is in agreement with the most precise determination from LEP and the Standard Model prediction based on three neutrino generations

    Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV Pb + Pb and pp Collisions with the ATLAS Detector

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    Determination of the Relative Sign of the Higgs Boson Couplings to W and Z Bosons Using WH Production via Vector-Boson Fusion with the ATLAS Detector

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    The associated production of Higgs and W bosons via vector-boson fusion is highly sensitive to the relative sign of the Higgs boson couplings to W and Z bosons. In this Letter, two searches for this process are presented, using 140 fb^{-1} of proton-proton collision data at sqrt[s]=13 TeV recorded by the ATLAS detector at the LHC. The first search targets scenarios with opposite-sign couplings of the W and Z bosons to the Higgs boson, while the second targets standard model-like scenarios with same-sign couplings. Both analyses consider Higgs boson decays into a pair of b quarks and W boson decays with an electron or muon. The data exclude the opposite-sign coupling hypothesis with a significance beyond 5σ, and the observed (expected) upper limit set on the cross section for vector-boson fusion WH production is 9.0 (8.7) times the standard model value at 95% confidence level

    Search for light long-lived neutral particles from Higgs boson decays via vector-boson-fusion production from pp collisions at s=13\sqrt{s}=13 TeV with the ATLAS detector

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    Search for heavy neutral Higgs bosons decaying into a top quark pair in 140 fb−1 of proton-proton collision data at s \sqrt{s} = 13 TeV with the ATLAS detector

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

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    In the version of this article initially published, the ATLAS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article

    Measurement of Higgs boson decay into b-quarks in associated production with a top-quark pair in pp collisions at √s = 13 TeV with the ATLAS detector

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    The associated production of a Higgs boson and a top-quark pair is measured in events characterised by the presence of one or two electrons or muons. The Higgs boson decay into a b-quark pair is used. The analysed data, corresponding to an integrated luminosity of 139 fb−1, were collected in proton-proton collisions at the Large Hadron Collider between 2015 and 2018 at a centre-of-mass energy of s = 13 TeV. The measured signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model, is 0.35−0.34+0.36. This result is compatible with the Standard Model prediction and corresponds to an observed (expected) significance of 1.0 (2.7) standard deviations. The signal strength is also measured differentially in bins of the Higgs boson transverse momentum in the simplified template cross-section framework, including a bin for specially selected boosted Higgs bosons with transverse momentum above 300 GeV. [Figure not available: see fulltext.

    Search for resonant WZ production in the fully leptonic final state in proton–proton collisions at √s=13 TeV with the ATLAS detector

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    A search for a WZ resonance, in the fully leptonic final state (electrons or muons), is performed using 139 fb - 1 of data collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The results are interpreted in terms of a singly charged Higgs boson of the Georgi–Machacek model, produced by WZ fusion, and of a Heavy Vector Triplet, with the resonance produced by WZ fusion or the Drell–Yan process. No significant excess over the Standard Model prediction is observed and limits are set on the production cross-section times branching ratio as a function of the resonance mass for these processes

    Studies of the Energy Dependence of Diboson Polarization Fractions and the Radiation-Amplitude-Zero Effect in WZ Production with the ATLAS Detector

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    : This Letter presents the first study of the energy dependence of diboson polarization fractions in WZ→lνl^{'}l^{'}(l,l^{'}=e,μ) production. The dataset used corresponds to an integrated luminosity of 140 fb^{-1} of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector. Two fiducial regions with an enhanced presence of events featuring two longitudinally polarized bosons are defined. A nonzero fraction of events with two longitudinally polarized bosons is measured with an observed significance of 5.3 standard deviations in the region with 100200 GeV, where p_{T}^{Z} is the transverse momentum of the Z boson. This Letter also reports the first study of the radiation-amplitude-zero effect. Events with two transversely polarized bosons are analyzed for the ΔY(l_{W}Z) and ΔY(WZ) distributions defined respectively as the rapidity difference between the lepton from the W boson decay and the Z boson and the rapidity difference between the W boson and the Z boson. Significant suppression of events near zero is observed in both distributions. Unfolded ΔY(l_{W}Z) and ΔY(WZ) distributions are also measured and compared to theoretical predictions

    Measurement of the polarisation of W bosons produced in top-quark decays using dilepton events at root s=13 TeV with the ATLAS experiment

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    A measurement of the polarisation of WW bosons produced in top-quark decays is presented, using proton-proton collision data at a centre-of-mass energy of s=13\sqrt{s} = 13 TeV. The data were collected by the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 139 fb1^{-1}. The measurement is performed selecting ttˉt\bar{t} events decaying into final states with two charged leptons (electrons or muons) and at least two bb-tagged jets. The polarisation is extracted from the differential cross-section distribution of the cosθ\cos{\theta^{*}} variable, where θ\theta^{*} is the angle between the momentum direction of the charged lepton from the WW boson decay and the reversed momentum direction of the bb-quark from the top-quark decay, both calculated in the WW boson rest frame. Parton-level results, corrected for the detector acceptance and resolution, are presented for the cosθ\cos{\theta^{*}} angle. The measured fractions of longitudinal, left- and right-handed polarisation states are found to be f0=0.684±0.005(stat.)±0.014(syst.)f_{0} = 0.684 \pm 0.005\,\mathrm{(stat.)} \pm 0.014\,\mathrm{(syst.)}, fL=0.318±0.003(stat.)±0.008(syst.)f_{\mathrm{L}} = 0.318 \pm 0.003\,\mathrm{(stat.)} \pm 0.008\,\mathrm{(syst.)} and fR=0.002±0.002(stat.)±0.014(syst.)f_{\mathrm{R}} = -0.002 \pm 0.002\,\mathrm{(stat.)} \pm 0.014\,\mathrm{(syst.)}, in agreement with the Standard Model prediction
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