%0 Generic
%A Klassen, Martin
%C Heidelberg
%D 2023
%F heidok:33952
%R 10.11588/heidok.00033952
%T Measurement of the Invisible Width of the Z Boson  with the ATLAS Detector
%U https://archiv.ub.uni-heidelberg.de/volltextserver/33952/
%X The measurement of the partial decay width of the Z boson into invisible particles represents a precision test of the electroweak structure of the Standard Model of particle physics. In this thesis, a measurement of the invisible Z boson width with the ATLAS detector at the Large Hadron Collider is presented using an integrated luminosity of 37 fb-1 of proton-proton collision data collected at a centre-of-mass energy of 13 TeV. Collision events with missing transverse momentum associated with at least one highly energetic jet are selected. Ratios of the obtained invisible Z boson decays to Z boson decays into pairs of oppositely charged electrons or muons, respectively, are constructed. These ratios are corrected for detector effects and combined into a ratio of branching fractions Rmiss. This ratio is then used in combination with the leptonic Z boson width, determined at the Large Electron-Positron Collider, to derive the invisible width of the Z boson. It is measured to be 506 ± 2 (stat.) ± 12 (syst.) MeV, which is in excellent agreement with the Standard Model prediction and with previous measurements. This result is the single most precise measurement of Γ_Z(inv) to date based on missing transverse momentum in the final state.