ttHH production in multilepton final states with the ATLAS experiment

Higgs boson pair production in association with a top-quark pair, ttHH, is a rare and unexplored process in the Standard Model with an expected cross-section 0.8 fb at 13 TeV. It is sensitive to BSM physics in the Higgs sector due to the Yukawa coupling of the Top quark. In addition, ttHH production provides a signature to probe Higgs self-coupling. A new analysis using ATLAS Run-2 and Run-3 data studies the ttHH sensitivity and the Higgs self-coupling constraints. In this talk, the sensitivity for an integrated luminosity of 140 fb−1 in Run2 will be presented. The ttHH decay final states containing either a pair of same-sign leptons or multi-lepton (SSML) are considered. Analysis strategies with novel techniques on multivariate analysis (ex. BDT, transformer), background modeling, and ttHH sensitivity will be discussed.