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Type: Journal article
Title: Study of heavy-flavor quarks produced in association with top-quark pairs at √s=7  TeV using the ATLAS detector
Other Titles: Study of heavy-flavor quarks produced in association with top-quark pairs at root s=7TeV using the ATLAS detector
Author: Aad, G.
ATLAS Collaboration
Citation: Physical Review D: Particles, Fields, Gravitation and Cosmology, 2014; 89(7):072012-1-072012-23
Publisher: American Physical Society
Issue Date: 2014
ISSN: 1550-2368
Statement of
G. Aad … P. Jackson … L. Lee … A. Petridis … N. Soni ... M. White ... et al. (ATLAS Collaboration)
Abstract: Using a sample of dilepton top-quark pair (tt -bar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of tt -bar+b+X and tt -bar+c+X, collectively referred to as tt -bar+HF. The data set used corresponds to an integrated luminosity of 4.7fb -1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the tt -bar sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the tt -bar decays and the third to additional HF production. The dominant background to tt -bar+HF in this sample is tt -bar+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79+/-14(stat)+/-22(syst) of the 105 selected extra b-tagged jets originate from HF quarks, 3 standard deviations away from the hypothesis of zero tt -bar+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for tt -bar+HF production to the cross section for tt -bar production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2+/-1.1(stat)+/-1.8(syst)]% for jets with pT>25GeV and |eta|<2.5, in agreement with the expectations from Monte Carlo generators.
Rights: © 2014 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.
DOI: 10.1103/PhysRevD.89.072012
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