@Article{ATLASCollaborationAad_etal2023, author="ATLAS Collaboration (Aad, G. et al and Amos, K. R. and Aparisi Pozo, J. A. and Bailey, A. J. and Bouchhar, N. and Cabrera Urban, S. and Cantero, J. and Cardillo, F. and Castillo Gimenez, V. and Chitishvili, M. and Costa, M. J. and Didenko and Escobar, C. and Fiorini, L. and Fullana Torregrosa, E. and Fuster, J. and Garcia, C. and Garcia Navarro, J. E. and Gomez Delegido, A. J. and Gonzalez de la Hoz, S. and Gonzalvo Rodriguez, G. R. and Guerrero Rojas, J. G. R. and Lacasta, C. and Marti-Garcia, S. and Martinez Agullo, P. and Miralles Lopez, M. and Mitsou, V. A. and Monsonis Romero, L. and Moreno Llacer, M. and Munoz Perez, D. and Navarro-Gonzalez, J. and Poveda, J. and Prades Iba{\~{n}}ez, A. and Rubio Jimenez, A. and Ruiz-Martinez, A. and Sabatini, P. and Salt, J. and Sanchez Sebastian, V. and Sayago Galvan, I. and Senthilkumar, V. and Soldevila, U. and Sanchez, J. and Torro Pastor, E. and Valero, A. and Valiente Moreno, E. and Valls Ferrer, J. A. and Varriale, L. and Villaplana Perez, M. and Vos, M.", title="Observation of four-top-quark production in the multilepton final state with the ATLAS detector", journal="European Physical Journal C", year="2023", publisher="Springer", volume="83", number="6", pages="496 - 35pp", abstract="This paper presents the observation of four-topquark (t (t) over bart (t) over bar) production in proton-proton collisions at the LHC. The analysis is performed using an integrated luminosity of 140 fb-1 at a centre-of-mass energy of 13 TeVcollected using the ATLAS detector. Events containing two leptons with the same electric charge or at least three leptons (electrons or muons) are selected. Event kinematics are used to separate signal from background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The observed (expected) significance of themeasured t (t) over bart (t) over bar signal with respect to the standard model (SM) background-only hypothesis is 6.1 (4.3) standard deviations. The t (t) over bart (t) over bar production cross section is measured to be 22.5(-5.5)(+6.6), consistent with the SM prediction of 12.0 +/- 2.4 fb within 1.8 standard deviations. Data are also used to set limits on the three-top-quark production cross section, being an irreducible background not measured previously, and to constrain the top-Higgs Yukawa coupling and effective field theory operator coefficients that affect t (t) over bart (t) over bar production.", optnote="WOS:001060591500001", optnote="exported from refbase (https://references.ific.uv.es/refbase/show.php?record=5724), last updated on Mon, 30 Oct 2023 16:04:17 +0000", issn="1434-6044", doi="10.1140/epjc/s10052-023-11573-0", opturl="https://arxiv.org/abs/2303.15061", opturl="https://doi.org/10.1140/epjc/s10052-023-11573-0", language="English" }