Constraining off-shell Higgs boson production and the Higgs boson total width using $WW\to \ellν\ellν$ final states with the ATLAS detector

Abstract: A measurement of off-shell Higgs boson production is performed in the $H^{*} \rightarrow WW$ channel. The measurement uses a proton-proton collision dataset with an integrated luminosity of 140 fb$^{-1}$ collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Final states in which both $W$ bosons decay leptonically are targeted, and events are categorised based on the flavour of the final-state leptons, the jet multiplicity, and the output of neural network-based classifiers. The data are found to be compatible with the Standard Model expectation. An observed (expected) upper limit at 95% confidence level is set on the rate of off-shell Higgs boson production at a value of 3.4 (4.4) times the Standard Model prediction. These results are combined with the results from the measurement of on-shell Higgs boson production with the same final states to obtain an observed (expected) upper limit at 95% confidence level on the Higgs boson total width of 13.1 (17.3) MeV.