Abstract
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 ∗, τ+τ−, γγ, and Z
Z∗, 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.) +110 (syst.) fb, in
agreement with the Standard Model prediction.
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