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

The recent progress on a search for four-top-quark production, $t\bar{t} t\bar{t}$, is presented based on data taken at $\sqrt{s}=13$ TeV with the ATLAS detector at the LHC. Data are analyzed in the single-lepton and opposite-sign dilepton channels. The search exploits the high jet / b-tagged jet multiplicities and large total sum of jet transverse momenta, which characterize signal events and provide good discrimination against the $t\bar{t}$ + jets dominant background, which is estimated through a data-driven method. The result is combined with the same-sign dilepton and multilepton final states search carried out by ATLAS.