摘要
This Letter reports on a search for off-shell production of the Higgs boson using 139\textrm{fb}{⁻¹}{}ofppcollision data at√s̅=13 TeV collected by the ATLAS detector at the Large Hadron Collider. The signature is a pair ofZbosons, with contributions from both the production and subsequent decay of a virtual Higgs boson and the interference of that process with other processes. The two observable final states areZZ→ 4ℓandZZ→ 2ℓ2νwithℓ = eorμ . In theZZ→ 4ℓfinal state, a dense Neural Network is used to enhance analysis sensitivity. The background-only hypothesis is rejected with an observed (expected) significance of 3.3 (2.2) standard deviations, representing experimental evidence for off-shell Higgs boson production. Assuming that no new particles enter the production of the virtual Higgs boson, its total width can be deduced from the measurement of its off-shell production cross-section. The measured total width of the Higgs boson is4.5^(+3.3)_(-2.5)MeV, and the observed (expected) upper limit on the total width is found to be 10.5 (10.9) MeV at 95% confidence level.