Electrical tests of silicon detector modules for the ATLAS experiment and a study of the discovery potential of the $t\overline{t}H, H \to W^{+}W^{-}$ process

The first part of this thesis was a contribution to the construction of the ATLAS Semiconductor Tracking detector (SCT). About 200 SCT endcap modules were assembled at the University of Freiburg. Before installation in the experiment, each module was subject to thorough testing in order to ensure their functionality within the ATLAS specifications. A large part of these tests concerned the electrical functionality of the readout electronics and the bias current behaviour of the sensors. The responsibility for the electrical characterization of the Freiburg modules was part of this thesis. To be suited for the analysis of physics processes, the signals measured in the detector need to be transferred into particle four-momenta, requiring the reconstruction and identification of different particle types. This thesis contributes to the physics object identification by a study of methods to separate isolated electrons from real electron background produced in the decays of heavy quarks. A standard set of four discriminating variables for the ATLAS experiment is identified and combined in a projective likelihood estimator and its separation power is evaluated in various analysis scenarios. The isolation likelihood tool is a powerful ingredient to the study of the ttH, H->WW channel, for which it has also been extended to muons. A study of the discovery potential of the channel is performed for a Standard Model Higgs boson, based on a full simulation of the ATLAS detector and assuming an integrated luminosity of 30 inverse fb and a proton-proton collision energy of 14 TeV. The most promising final state, consisting of a pair of equally charged leptons, accompanied by six jets is studied. It is shown that the irreducible top quark pair production and W+jets backgrounds can be effectively suppressed. Uncertainties are discussed as well as discovery significances and the potential of the channel to contribute to a determination of the top quark Yukawa coupling.