Towards Precision Measurments in the Standard Model with the ATLAS detector

Standard Model Processes will be useful in the early phase of the LHC program, because they benefit from a large production cross section and have relatively firm production predictions. With an integrated luminosity of a few pb-1, many Z's, W's, direct photons and jets will be recorded so that the detector response to leptons, photons, jets and missing $E_T$ can be studied. From the physics point of view, standard model processes will help to constrain parton density functions and the properties of underlying events at the energy of the LHC. Standard model processes, for example, W+jets, can produce large backgrounds to search channels for physics beyond the standard model, so precise measurement of these processes is a necessary prerequisite for the discovery of new physics. New physics can manifest itself in standard model processes, for example, high transverse momentum jets probe a qqqq contact interaction, and diboson production is sensitive to couplings that differ from the electroweak predictions. A precise measurement of the W mass is sensitive to new particles in loops, and will serve to constrain them.