Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector

Abstract

The observation of Higgs boson production in association with a top quark pair (tt¯H), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb?1, and considering Higgs boson decays into bb¯, WW?, ?+??, ??, and ZZ?, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the tt¯H searches using a dataset corresponding to integrated luminosities of 4.5 fb?1 at 7 TeV and 20.3 fb?1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total tt¯H production cross section at 13 TeV is measured to be 670 ± 90 (stat.) ?100 +110 (syst.) fb, in agreement with the Standard Model prediction. © 2018 The Author(s)