EARLY STANDARD MODEL MEASUREMENTS WITH ATLAS

We present prospects to perform early measurements of the production cross-section of the electroweak bosons and of top pairs with the ATLAS detector at LHC. An accurate determination of these cross-sections provide a valuable test of the Standard Model. The W and Z analyses exploit the leptonic decays in electrons and muons; the top pair production is studied using final states in which one or both top quark decay semileptonically. Given the high production cross-section at 14 TeV of electroweak bosons and of top quark pairs and the high luminosity of the LHC accelerator, these particles are expected to be produced abundantly. This fact together with the rather distinct event topology makes these measurements possible already after that few tenths of inverse picobarn of luminosity are recorded. For this reason emphasis will be given to data-driven methods used to extract trigger and lepton reconstruction efficiencies and to reject backgrounds. For the same reason, in the top pair production study, when only one of the top quark decays semileptonically we perform the cross-section measurement with and without relying on the tagging of b-quark initiated jets.