Precision measurement of the Z boson invisible width in pp collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports the most precise direct measurement of the Z boson's invisible width at a hadron collider, using CMS data at 13 TeV, achieving results comparable to LEP experiments.

Contribution

First precise measurement of the Z boson invisible width at a hadron collider using a novel simultaneous fit method with CMS data.

Findings

Invisible width measured as 523 ± 3 (stat) ± 16 (syst) MeV

Achieved the most precise direct measurement to date

Results are competitive with LEP measurements

Abstract

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 $\pm$ 3 (stat) $\pm$ 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.