Measurement of $W^{\pm }$ and $Z$-boson production cross sections in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

Measurements of the $W^{\pm }\to {\ell }^{\pm }\nu$ 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 Large Hadron Collider, corresponding to a total integrated luminosity of 81 pb${}^{-1}$ The total inclusive $W^{\pm }$-boson production cross sections times the single-lepton-flavour branching ratios are ${\sigma }_{W^{+}}^{tot}=11.83\pm 0.02(stat)\pm 0.32(sys)\pm 0.25(lumi)$ nb and ${\sigma }_{W^{-}}^{tot}=8.79\pm 0.02(stat)\pm 0.24(sys)\pm 0.18(lumi)$ nb for $W^{+}$ and $W^{-}$, respectively. The total inclusive $Z$-boson production cross section times leptonic branching ratio, within the invariant mass window $66<m_{\ell \ell }<116$ GeV, is ${\sigma }_Z^{tot}=1.981\pm 0.007(stat)\pm 0.038(sys)\pm 0.042(lumi)$ 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 ${\sigma }_{W^{+}}^{fid}/{\sigma }_{W^{-}}^{fid}=1.295\pm 0.003(stat)\pm 0.010(sys)$ and ${\sigma }_{W^{\pm }}^{fid}/{\sigma }_Z^{fid}=10.31\pm 0.04(stat)\pm 0.20(sys)$. 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.

Comments: 17 pages plus author list + cover pages (34 pages total), 5 figures, 3 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-03/