First measurements of the W → ℓν and Z/γ* → ℓℓ (ℓ = e; μ) production cross sections in proton-proton collisions at √s = 7TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W → ℓν and 179 Z/γ* → ℓℓ candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/γ*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are σtot W. BR(W → ℓν) = 9.96± 0.23(stat)±0.50(syst)±1.10(lumi) nb and σtot Z/γ*. BR(Z/γ* → 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.La lista completa de autores puede verse al final del archivo asociado.Facultad de Ciencias Exactas