# Evidence for $t\bar{t}t\bar{t}$ production in the multilepton final state in proton-proton collisions at $\sqrt{s}$=13 TeV with the ATLAS detector

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## Abstract

A search is presented for four-top-quark production using an integrated luminosity of 139 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be 24$^{+7}_{-6}$ fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process.

## Bibliographic note

45 pages total, author list starting page 29, 7 figures, 4 tables, published in EPJC. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-05/

## Details

Original language English 1085 Eur. Phys. J. C 80 Published - 30 Nov 2020

• hep-ex