ATLAS Collab.
A precise determination of the strong-coupling constant from the recoil of Z bosons with the ATLAS experiment at √s=8 TeV
The coupling constant of the strong force is determined from the transverse-momentum distribution of Z bosons produced in 8 TeV proton-proton collisions at the LHC and recorded by the ATLAS experiment. The Z-boson cross sections are measured in the full phase space of the decay leptons using 15.3 million electron and muon pairs, in a dataset collected in 2012 and corresponding to an integrated luminosity of 20.2 fb−1. The analysis is based on predictions evaluated at third order in perturbative QCD, supplemented by the resummation of logarithmically enhanced contributions in the low transverse-momentum region of the lepton pairs. The determined value of the strong coupling at the reference scale corresponding to the Z-boson mass is αs(mZ)=0.1183±0.0009. This is the most precise experimental determination of αs(mZ) achieved so far.