Yazar "Ting, E.X.L." seçeneğine göre listele

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    Measurement of the production of a W boson in association with a charmed hadron in pp collisions at ?s=13 TeV with the ATLAS detector
    (American Physical Society, 2023) Filmer, E.K.; Jackson, P.; Kong, A.X.Y.; Potti, H.; Ruggeri, T.A.; Ting, E.X.L.; Çetin, Serkant Ali
    The production of a W boson in association with a single charm quark is studied using 140 fb - 1 of s = 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The charm quark is tagged by the presence of a charmed hadron reconstructed with a secondary-vertex fit. The W boson is reconstructed from the decay to either an electron or a muon and the missing transverse momentum present in the event. The charmed mesons reconstructed are D + ? K - ? + ? + and D * + ? D 0 ? + ? ( K - ? + ) ? + and the charge conjugate decays in the fiducial regions where p T ( e , ? ) > 30 GeV , | ? ( e , ? ) | < 2.5 , p T ( D ( * ) ) > 8 GeV , and | ? ( D ( * ) ) | < 2.2 . The integrated and normalized differential cross sections as a function of the pseudorapidity of the lepton from the W boson decay, and of the transverse momentum of the charmed hadron, are extracted from the data using a profile likelihood fit. The measured total fiducial cross sections are ? fid OS - SS ( W - + D + ) = 50.2 ± 0.2 ( stat ) - 2.3 + 2.4 ( syst ) pb , ? fid OS - SS ( W + + D - ) = 48.5 ± 0.2 ( stat ) - 2.2 + 2.3 ( syst ) pb , ? fid OS - SS ( W - + D * + ) = 51.1 ± 0.4 ( stat ) - 1.8 + 1.9 ( syst ) pb , and ? fid OS - SS ( W + + D * - ) = 50.0 ± 0.4 ( stat ) - 1.8 + 1.9 ( syst ) pb . Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. Additionally, the ratio of charm to anticharm production cross sections is studied to probe the s - s ¯ quark asymmetry. The ratio is found to be R c ± = 0.971 ± 0.006 ( stat ) ± 0.011 ( syst ) . The ratio and cross-section measurements are consistent with the predictions obtained with parton distribution function sets that have a symmetric s - s ¯ sea, indicating that any s - s ¯ asymmetry in the Bjorken- x region relevant for this measurement is small. © 2023 CERN, for the ATLAS Collaboration.
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    Measurements of the suppression and correlations of dijets in Xe+Xe collisions at Formula Presented TeV
    (American Physical Society, 2023) Filmer, E.K.; Jackson, P.; Kong, A.X.Y.; Potti, H.; Ruggeri, T.A.; Ting, E.X.L.; Çetin, Serkant Ali
    Measurements of the suppression and correlations of dijets is performed using 3 µ b ? 1 of Xe+Xe data at s N N = 5.44 TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Dijets with jets reconstructed using the R = 0.4 anti- k t algorithm are measured differentially in jet p T over the range of 32 to 398 GeV and the centrality of the collisions. Significant dijet momentum imbalance is found in the most central Xe+Xe collisions, which decreases in more peripheral collisions. Results from the measurement of per-pair normalized and absolutely normalized dijet p T balance are compared with previous Pb + Pb measurements at s N N = 5.02 TeV. The differences between the dijet suppression in Xe+Xe and Pb + Pb are further quantified by the ratio of pair nuclear-modification factors. The results are found to be consistent with those measured in Pb + Pb data when compared in classes of the same event activity and when taking into account the difference between the center-of-mass energies of the initial parton scattering process in Xe+Xe and Pb + Pb collisions. These results should provide input for a better understanding of the role of energy density, system size, path length, and fluctuations in the parton energy loss. ©2023 CERN, for the ATLAS Collaboration.
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    Search for displaced photons produced in exotic decays of the Higgs boson using 13 TeV pp collisions with the ATLAS detector
    (American Physical Society, 2023) Filmer, E.K.; Jackson, P.; Kong, A.X.Y.; Potti, H.; Ruggeri, T.A.; Ting, E.X.L.; Çetin, Serkant Ali
    A search is performed for delayed and nonpointing photons originating from the displaced decay of a neutral long-lived particle (LLP). The analysis uses the full run 2 dataset of proton-proton collisions delivered by the LHC at a center-of-mass energy of Formula Presented between 2015 and 2018 and recorded by the ATLAS detector, corresponding to an integrated luminosity of Formula Presented. The capabilities of the ATLAS electromagnetic calorimeter are exploited to precisely measure the arrival times and trajectories of photons. The results are interpreted in a scenario where the LLPs are pair produced in exotic decays of the 125 GeV Higgs boson, and each LLP subsequently decays into a photon and a particle that escapes direct detection, giving rise to missing transverse momentum. No significant excess is observed above the expectation due to Standard Model background processes. The results are used to set upper limits on the branching ratio of the exotic decay of the Higgs boson. A model-independent limit is also set on the production of photons with large values of displacement and time delay. © 2023 CERN, for the ATLAS Collaboration.