Search for four-top-quark production in the single-lepton and opposite-sign dilepton final states in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Abstract

A search for four-top-quark production, $t\bar{t}t\bar{t}$, is presented. It is based on proton-proton collision data with a center-of-mass energy $\sqrt{s}$ = 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the year 2015 and 2016, corresponding to an integrated luminosity of $36.1$ fb${}^{-1}$. Data are analyzed in both the single-lepton and opposite-sign dilepton channels, characterized by the presence of one or two isolated electrons or muons with high-transverse momentum and multiple jets. A data-driven method is used to estimate the dominant background from top-quark pair production in association with jets. No significant excess above the Standard Model expectation is observed. The result is combined with the previous same-sign dilepton and multilepton searches carried out by ATLAS and an observed (expected) upper limit of 5.3 (2.1) times the four-top-quark Standard Model cross section is obtained at 95% confidence level. Additionally, upper limit on anomalous four-top-quark production cross section is set in the context of an effective field theory model.

54 pages in total, author list starting page 38, 11 figures, 2 tables, submitted to Phys. Rev. D. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2017-11

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• Measurement of the $\mathrm{t}\bar{\mathrm{t}}\mathrm{b}\bar{\mathrm{b}}$ production cross section in the all-jet final state in pp collisions at $\sqrt{s}=$ 13 TeV
• Search for the production of four top quarks in the single-lepton and opposite-sign dilepton final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Measurement of the $t\bar{t}t\bar{t}$ production cross section in $pp$ collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
• Implications of Four-Top and Top-Pair Studies on Triple-Top Production
• Modeling uncertainties of $t\bar{t}{W}^{\pm }$ multilepton signatures
• Effective field theory and scalar extensions of the top quark sector
• $W$ mass in a model with vector-like leptons and $U(1{)}^{\prime }$
• On the BSM reach of four top production at the LHC
• Search for phenomena beyond the Standard Model in events with large $b$-jet multiplicity using the ATLAS detector at the LHC
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• Top-pair production via gluon fusion in the Standard Model Effective Field Theory
• Hadroproduction of four top quarks in the POWHEG BOX
• $t\bar{t}$ + $Z$ / $W$ / $t\bar{t}$ at ATLAS