Prospects of a cross section ratio measurement of W and Z events as a function of the jet multiplicity with early ATLAS data

The production of W and Z bosons in association with jets plays an important role at the ATLAS experiment at the "Large Hadron Collider (LHC)" situated at the "European Organization for Nuclear Research" CERN (Geneva, Switzerland). The work presented in this thesis prepared the measurement of the cross section ratio of W and Z events as a function of the jet multiplicity. This cross section ratio is needed to improve the W+jets normalization for top quark analyses and to test Monte Carlo generator and QCD predictions. It focused on a measurement using early ATLAS data. The idea of this analysis is to use the compatible event structures of W+jets and Z+jets events to estimate W+jets events from the easy selectable Z+jets event. Hence, first the event structures of W and Z events were compared proving that the event structures are very similar. Then a measurement of the cross section ratio was prepared. The consequences of systematic uncertainties on the measurement were also tested. In a final step the W+jets and Z+jets distributions were corrected for detector and reconstruction effects to be able to compare QCD calculations directly to the results.