Measurement Of The Ratio Of The W And Z Cross Sections With Exactly One Associated Jet In Pp Collisions At (?)=7TeV With ATLAS

In this thesis an investigation of the ratio of the production cross section of W and Z bosons in association with one jet at LHC is performed.The cross-section ratio is measured with LHC proton-proton collision data at a center-of-mass energy of7TeV, collected by the ATLAS experiment in2010, corresponding to an integrated luminosity of approximately40pb-1. The analysis is performed selecting W and Z bosons decaying in the muon channel.It is the first time the ratio of W and Z bosons production associated with one jet is measured at such a high center-of-mass energy, the measurement is the first one at the LHC. This measurement constitutes a very important test of perturbative theoretical calculations based on the advantage of the partial and full cancellations of various uncer-tainties.It also serves as constraining backgrounds with similar topological signatures in the search for new physics phenomena at the LHC.The measured ratio value is presented as a function of cumulative jet transverse mo-mentum thresholds and found, within statistical precision, to agree well with perturbative LO and NLO QCD predictions.