Examinando por Autor "Abramowicz, H"

Mostrando 1 - 4 de 4
  • Miniatura
    Ítem
    Measurement of azimuthal anisotropy of muons from charm and bottom hadrons in Pb+Pb collisions at sNN=5.02 TeV with the ATLAS detector
    (Elsevier B.V., 2020-08) Aad, G; Abbott, B; Abbott, D.C; Abed Abud, A; Abeling, K; Abhayasinghe, D.K.; Abidi, S.H.; AbouZeid ., O.S; Abraham, N.L; Abramowicz, H; Abreu, H; Abulaiti, Y
    Azimuthal anisotropies of muons from charm and bottom hadron decays are measured in Pb+Pb collisions at sNN=5.02TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2018 with integrated luminosities of 0.5nb−1 and 1.4nb−1, respectively. The kinematic selection for heavy-flavor muons requires transverse momentum 4T<30GeV and pseudorapidity |η|<2.0. The dominant sources of muons in this pT range are semi-leptonic decays of charm and bottom hadrons. These heavy-flavor muons are separated from light-hadron decay muons and punch-through hadrons using the momentum imbalance between the measurements in the tracking detector and in the muon spectrometers. Azimuthal anisotropies, quantified by flow coefficients, are measured via the event-plane method for inclusive heavy-flavor muons as a function of the muon pT and in intervals of Pb+Pb collision centrality. Heavy-flavor muons are separated into contributions from charm and bottom hadron decays using the muon transverse impact parameter with respect to the event primary vertex. Non-zero elliptic (v2) and triangular (v3) flow coefficients are extracted for charm and bottom muons, with the charm muon coefficients larger than those for bottom muons for all Pb+Pb collision centralities. The results indicate substantial modification to the charm and bottom quark angular distributions through interactions in the quark-gluon plasma produced in these Pb+Pb collisions, with smaller modifications for the bottom quarks as expected theoretically due to their larger mass. © 2020 The Author(s)
  • Miniatura
    Ítem
    Measurement of isolated-photon plus two-jet production in pp collisions at p s = 13TeV with the ATLAS detector
    (Springer, 2020-03) Aad, G.; Abbott, B.; Abbott, D.C.; Abed Abud, A.; Abeling ., K; Abhayasinghe, D.K; Abidi, S.H; AbouZeid, O.S; Abraham, N.L; Abramowicz, H; Abreu, H; Abulaiti, Y
    The dynamics of isolated-photon plus two-jet production in "padding-size-4-x display--inline-block" style="background: var(--highlight-yellow); color: inherit;">pp collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset corresponding to an integrated luminosity of 36.1 fb−1. Cross sections are measured as functions of a variety of observables, including angular correlations and invariant masses of the objects in the final state, γ + jet + jet. Measurements are also performed in phase-space regions enriched in each of the two underlying physical mechanisms, namely direct and fragmentation processes. The measurements cover the range of photon (jet) transverse momenta from 150 GeV (100 GeV) to 2 TeV. The tree-level plus parton-shower predictions from Sherpa and Pythia as well as the next-to-leading-order QCD predictions from Sherpa are compared with the measurements. The next-to-leading-order QCD predictions describe the data adequately in shape and normalisation except for regions of phase space such as those with high values of the invariant mass or rapidity separation of the two jets, where the predictions overestimate the data. [Figure not available: see fulltext.] © 2020, The Author(s).
  • Miniatura
    Ítem
    Measurement of the Lund Jet Plane Using Charged Particles in 13 TeV Proton-Proton Collisions with the ATLAS Detector
    (American Physical Society, 2020-06) Aad, G.; Abbott, B.; Abbott, D.C; Abed Abud, A; Abeling, K; Abhayasinghe, D.K.; Abidi, S.H.; Abouzeid, O.S; Abraham, N.L.; Abramowicz, H; Abreu, H.; Abulaiti, Y.
    The prevalence of hadronic jets at the LHC requires that a deep understanding of jet formation and structure is achieved in order to reach the highest levels of experimental and theoretical precision. There have been many measurements of jet substructure at the LHC and previous colliders, but the targeted observables mix physical effects from various origins. Based on a recent proposal to factorize physical effects, this Letter presents a double-differential cross-section measurement of the Lund jet plane using 139 fb-1 of s=13 TeV proton-proton collision data collected with the ATLAS detector using jets with transverse momentum above 675 GeV. The measurement uses charged particles to achieve a fine angular resolution and is corrected for acceptance and detector effects. Several parton shower Monte Carlo models are compared with the data. No single model is found to be in agreement with the measured data across the entire plane. © 2020 CERN.
  • Miniatura
    Ítem
    Search for new resonances in mass distributions of jet pairs using 139 fb −1 of pp collisions at √s = 13 TeV with the ATLAS detector
    (Springer, 2020-03) Aad, G.; Abbott, B.; Abbott, D.C; Abed Abud, A.; Abeling, K.; Abhayasinghe, D.K.; Abidi, S.H.; AbouZeid, O.S; Abraham ., N.L; Abramowicz, H; Abreu, H; Abulaiti, Y.
    A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at s = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb−1. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the Standard Model background. In addition to an inclusive dijet search, events with jets identified as containing b-hadrons are examined specifically. No significant excess of events above the smoothly falling background spectra is observed. The results are used to set cross-section upper limits at 95% confidence level on a range of new physics scenarios. Model-independent limits on Gaussian-shaped signals are also reported. The analysis looking at jets containing b-hadrons benefits from improvements in the jet flavour identification at high transverse momentum, which increases its sensitivity relative to the previous analysis beyond that expected from the higher integrated luminosity. [Figure not available: see fulltext.] © 2020, The Author(s).