A precise measurement of the invisible width of the Z boson produced in proton-proton collisions at a
center-of-mass energy of 13 TeV is presented using data recorded by the CMS experiment at the LHC,
corresponding to an integrated luminosity of 36.3 fb−1 . The result is obtained from a simultaneous fit to
kinematic distributions for two data samples of Z boson plus jets: one dominated by Z boson decays to
invisible particles and the other by Z boson decays to muon and electron pairs. The invisible width is
measured to be 523 ± 3 (stat) ± 16 (syst) MeV. This result is the first precise measurement of the invisible
width of the Z boson at a hadron collider, and is the single most precise direct measurement to date,
competitive with the combined result of the direct measurements from the LEP experiments.