Measurement of W and Z Boson Production Cross Sections in pp Collisions at root s = 13 TeV in the ATLAS Detector

Measurements of the $W \to \ell^{\pm} \nu$ and $Z\to\ell^+\ell^-$ production cross sections (where $\ell^{\pm}=e^{\pm},\mu^{\pm}$) in proton-proton collisions at $\sqrt{s}=13$ TeV are presented using data recorded by the ATLAS experiment at the LHC, corresponding to a total integrated luminosity of approximately 85 pb$^{-1}$. The total inclusive $W^\pm$ boson production cross sections times the single-lepton-flavour branching ratios are $\sigma^\text{tot}_{W^+}$=[10960±20(stat)±440(sys)±990(lumi)] pb and $\sigma^\text{tot}_{W^+}$=[8380±20(stat)±350(sys)±750(lumi)] pb for $W^+$ and $W^-$ respectively. The total inclusive $Z$ boson production cross section times leptonic branching ratio, within the invariant mass window 66 < $m_{\ell\ell}$ < 116 GeV}, is $\sigma^\text{tot}_Z$=[1869±7(stat)±42(sys)±168(lumi)] pb. The $W^+$, $W^-$, and $Z$ boson production cross sections and cross-section ratios are also measured within a fiducial region defined by the detector acceptance. Theoretical predictions based on calculations accurate to NLO for electroweak and NNLO for QCD, using different PDF sets and predictions from different Monte Carlo generators, are compared to the measurements.