Measurement of And -boson Production Cross Sections in Collisions at with the ATLAS detector

Measurements of the ${W}^{±}\to {\ell }^{±}\nu $ and $Z\to {\ell }^{+}{\ell }^{-}$ production cross sections (where ${\ell }^{±}={e}^{±},{\mu }^{±}$) in proton–proton collisions at $\sqrt{s}=13\text{TeV}$ are presented using data recorded by the ATLAS experiment at the Large Hadron Collider, corresponding to a total integrated luminosity of 81 pb$^{−1}$. The total inclusive ${W}^{±}$-boson production cross sections times the single-lepton-flavour branching ratios are ${\sigma }_{{W}^{+}}^{\mathrm{tot}}=11.83±0.02\text{}\text{(stat)}±0.32\text{}\text{(sys)}±0.25\text{}\text{(lumi)}\text{nb}$ and ${\sigma }_{{W}^{-}}^{\mathrm{tot}}=8.79±0.02\text{}\text{(stat)}±0.24\text{}\text{(sys)}±0.18\text{}\text{(lumi)}\text{nb}$ for ${W}^{+}$ and ${W}^{-}$, respectively. The total inclusive Z-boson production cross section times leptonic branching ratio, within the invariant mass window $66<{m}_{\ell \ell }<116\text{GeV}$, is ${\sigma }_{Z}^{\text{tot}}=1.981±0.007\text{}\text{(stat)}±0.038\text{}\text{(sys)}±0.042\text{}\text{(lumi)}\text{nb}$. The ${W}^{+}$, ${W}^{-}$, and Z-boson production cross sections and cross-section ratios within a fiducial region defined by the detector acceptance are also measured. The cross-section ratios benefit from significant cancellation of experimental uncertainties, resulting in ${\sigma }_{{W}^{+}}^{\mathrm{fid}}/{\sigma }_{{W}^{-}}^{\mathrm{fid}}=1.295±0.003\text{}\text{(stat)}±0.010\text{}\text{(sys)}$ and ${\sigma }_{{W}^{±}}^{\mathrm{fid}}/{\sigma }_{Z}^{\mathrm{fid}}=10.31±0.04\text{}\text{(stat)}±0.20\text{}\text{(sys)}$. Theoretical predictions, based on calculations accurate to next-to-next-to-leading order for quantum chromodynamics and to next-to-leading order for electroweak processes and which employ different parton distribution function sets, are compared to these measurements.