Search for the Standard Model Higgs Boson in Decays into Four Charged Leptons with the ATLAS Detector at the LHC

In summer 2012, the ATLAS and CMS experiments at the Large Hadron Collider (LHC) announced the discovery of a new boson with the properties of the Standard Model Higgs boson. A significant signal was observed at a mass of about 125 GeV in three different decay channels. One of them is the decay channel $H \rightarrow ZZ^{(*)} \rightarrow 4l$. This thesis focuses on the study and selection of Higgs boson decays $H \rightarrow ZZ^{(*)} \rightarrow 4l$ with the ATLAS detector with data taken in 2011 and 2012. In particular, the precise measurement of the mass of the discovered boson in this decay channel are discussed. The Higgs boson mass measurement is described with focus on $H \rightarrow ZZ^{(*)} \rightarrow 4\mu$ decays. The baseline fit method for the Higgs boson mass measurement uses Monte Carlo generated templates. An alternative method using an analytical fit function has been successfully developed for Higgs mass measurement with the $H \rightarrow ZZ^{(*)} \rightarrow 4\mu$ channel. For the analytical fit function, corrections to the muon momentum resolution and muon momentum scale were necessary. Therefore, a method to incorporate muon momentum resolution and muon momentum scale corrections is presented.