Study of heavy-flavor quarks produced in association with top-quark pairs at using the ATLAS detector
Using a sample of dilepton top-quark pair (t$$\bar{t}$$) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of t$$\bar{t}$$+b+X and t$$\bar{t}$$+c+X, collectively referred to as t$$\bar{t}$$+HF. The data set used corresponds to an integrated luminosity of 4.7 fb-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 t$$\bar{t}$$ sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the t$$\bar{t}$$decays and the third to additional HF production. The dominant background to t$$\bar{t}$$+HF in this sample is t$$\bar{t}$$+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 t$$\bar{t}$$+HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for t$$\bar{t}$$+HF production to the cross section for t$$\bar{t}$$ 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 |η|<2.5, in agreement with the expectations from Monte Carlo generators.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Contributing Organization:
- ATLAS Collaboration
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1523929
- Journal Information:
- Physical Review. D, Particles, Fields, Gravitation and Cosmology, Vol. 89, Issue 7; ISSN 1550-7998
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Top-quark physics at the Large Hadron Collider
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journal | May 2017 |
Measurements of fiducial cross-sections for $$t\bar{t}$$ t t ¯ production with one or two additional b-jets in pp collisions at $$\sqrt{s}$$ s =8 TeV using the ATLAS detector
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journal | January 2016 |
Top-quark physics at the Large Hadron Collider | text | January 2016 |
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