Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector

First measurements of the W->lnu and Z/gamma(*)->ll (l=e,mu ) production cross sections in proton-proton collisions at sqrt(s) = 7TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W->lnu and 179 Z/gamma(*)->ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma(*)-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are sigma^tot_W x BR(W->lnu) = 9.96+-0.23(stat)+-0.50(syst)+-1.10(lumi) nb and sigma^tot_Z/gamma(*) x BR(Z/gamma(*)->ll) = 0.82+-0.06 (stat)+-0.05 (syst)+-0.09 (lumi) nb (within the invariant mass window 66 < mll < 116 GeV). The W/Z cross-section ratio is measured to be 11.7+-0.9(stat)+-0.4(syst). In addition, measurements of the W+ and W- production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.