Precision measurement of the Z boson invisible width in pp collisions at TeV

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$\phantom{\rule{0.2em}{0ex}}{\text{fb}}^{-1}$. 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 $523±3\phantom{\rule{0.2em}{0ex}}\text{(stat)}±16\phantom{\rule{0.2em}{0ex}}\text{(syst)}\phantom{\rule{0.2em}{0ex}}\text{MeV}$. 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.