Measurements of inclusive and associated jet W and Z production with the ATLAS detector

The production of the W and Z bosons is a standard candle process at the LHC. Precise total cross section measurements, in the fiducial region of the measurement and extrapolated to full phase space are presented. The differential Z/gamma∗ and the charge dependent W+ and W­ cross sections are provided in bins of boson rapidity and lepton pseudorapidity, respectively. The results are compared to Monte Carlo simulations and to predictions computed at NNLO QCD for different NNLO sets of parton distribution functions. A measurement of angular correlations in Drell–Yan lepton pairs for neutral current process via the phi* observable is also presented. This variable probes the same physics as the Z/gamma* boson transverse momentum (pT) with a better experimental resolution, especially for low transverse momenta. The measurement using phi* and the direct measurement of pT are compared to predictions based on QCD calculations and predictions from different Monte Carlo event generators. The production of jets in association with a W or Z boson in proton­proton collisions at 7 TeV represent an important process to study QCD in a multi­scale environment. The cross sections, differential in several kinematics variables, have been measured up to high jet multiplicities and compared to new higher­order QCD calculations. The ratio of (Z + a single jet)/(W + a single jet) can provide a very precise test of QCD and has also been measured. Overall, the cross sections demonstrate the need for the inclusion of higher­multiplicity matrix elements in the calculations, even in cases where a parton shower simulation is present.