With a value of about 4 MeV, the total width of the Higgs boson in the Standard Model is not accessible via direct measurements at the LHC as the experimental resolution is around 1 GeV.
Instead, a comparison of off-shell and on-shell Higgs boson production can reveal the value of the width under mild assumptions on the Higgs boson couplings. This seminar presents a new measurement of the Higgs boson off-shell production and its natural width based on the full Run 2 pp dataset collected at 13 TeV. The measurement exploits the gluon-fusion and vector-boson fusion production modes, and the decays channels into ZZ→4l and ZZ→2l2v. The background-only hypothesis is rejected with an observed (expected) significance of 3.2 (2.4) 𝜎, which marks the experimental evidence of off-shell Higgs production.