Study of the associated production of a Z boson and jets in pp collisions at $\sqrt{s}$ = 7 TeV at CMS

In this thesis differential cross sections measurements of Z boson and jets associated production (Z + jets) will be presented; they are obtained by analyzing a large part of the 2011 dataset that corresponds to a total integrated luminosity of 4.89 1/fb. This type of processes are central in the physics program of LHC. The study of jets produced with Z provides a stringent and important test of perturbative QCD. In addition, a precise measurement of the Z + jets cross sections is crucial since these processes are a significant background in searches for new physics. This work is organized as follows. First an introduction to the SM theory, to the Z + jets physics and to the Monte Carlo generators is given, then a summary of the main features of the CMS detector is presented. The description of how the reconstruction and the identification of the particles is done in CMS, with a particular attention to the electron and jets, is reported, followed by the discussion about the performance of the electron reconstruction algorithms used in CMS. Finally the measurement of the differential cross sections for the Z + jets associated production and the obtained results are described.