Measurement of the tt¯tt¯ production cross section in pp collisions at √s = 13 TeV with the ATLAS detector Atlas Collaboration Aguilar Saavedra, Juan Antonio Rodríguez Chala, Mikael Hadron-Hadron scattering (experiments) Top physics We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (U.K.) and BNL (U.S.A.), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in ref. A measurement of four-top-quark production using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider corresponding to an integrated luminosity of 139 fb−1 is presented. Events are selected if they contain a single lepton (electron or muon) or an opposite-sign lepton pair, in association with multiple jets. The events are categorised according to the number of jets and how likely these are to contain b-hadrons. A multivariate technique is then used to discriminate between signal and background events. The measured four-top-quark production cross section is found to be 26−15+17 fb, with a corresponding observed (expected) significance of 1.9 (1.0) standard deviations over the background-only hypothesis. The result is combined with the previous measurement performed by the ATLAS Collaboration in the multilepton final state. The combined four-top-quark production cross section is measured to be 24−6+7 fb, with a corresponding observed (expected) signal significance of 4.7 (2.6) standard deviations over the background-only predictions. It is consistent within 2.0 standard deviations with the Standard Model expectation of 12.0 ± 2.4 fb. 2022-01-18T12:14:29Z 2022-01-18T12:14:29Z 2021-11-16 journal article The ATLAS collaboration., Aad, G., Abbott, B. et al. Measurement of the tt¯tt¯ production cross section in pp collisions at s√ = 13 TeV with the ATLAS detector. J. High Energ. Phys. 2021, 118 (2021). [https://doi.org/10.1007/JHEP11(2021)118] http://hdl.handle.net/10481/72383 10.1007/JHEP11(2021)118 eng http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España Springer