Early Physics Reach of the ATLAS Detector

The first year of data taking at ATLAS will be a very challenging and promising time. It will consist of the commissioning of the detector and already many interesting physics results. The commissioning of the detector components will mainly rely on physics signals and reach the desired precision of 0.02\% for most subdetectors with the data of only a few weeks at low luminosity. The staging of some subdetectors will mainly influence the B physics program and result in slightly reduced significances in most physics analyses. The search for Higgs bosons and supersymmetric particles has been studied in great detail. If a Higgs boson from the Standard model exists, it will be discovered within the first year. If supersymmetry exists the discovery of one or even more Higgs bosons in the first year is very probable. The supersymmetric partners of the quarks and gluons could be produced with very large rates at the LHC and a discovery for masses above 2~TeV is possible within the first year.