Measurement of the inclusive W and Z production cross sections in pp collisions at $ \sqrt {s} = 7 $ TeV with the CMS experiment

A measurement of inclusive W and Z production cross sections in pp collisions at s = 7 TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb -1 . The measured inclusive cross sections are (pp WX) B(W ) = 10.31 0.02 (stat.) 0.09 (syst.) 0.10 (th.) 0.41 (lumi.) nb and (pp ZX) B(Z + -) = 0.974 0.007 (stat.) 0.007 (syst.) 0.018 (th.) 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are ((pp WX) B(W )) / ((pp ZX) B(Z + -)) = 10.54 0.07 (stat.) 0.08 (syst.) 0.16 (th.) and ((pp W + X) B(W + + )) / ((pp W -X) B(W - -)) = 1.421 0.006 (stat.) 0.014 (syst.) 0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions.