Implementation of trigger algorithms and studies for the measurement of the Higgs boson self-coupling in the ATLAS experiment at the LHC

At the LHC in Geneva the ATLAS experiment will start at 2007. The first part of the present work describes the implementation of trigger algorithms for the Jet/Energy Processor (JEP) as well as all other required features like controlling, diagnostics and read-out. The JEP is one of three processing units of the ATLAS Level-1 Calorimeter Trigger. It identifies and finds the location of jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the JEP. The JEM prototype is designed to be functionally identical to the final production module for ATLAS. The thesis presents a description of the architecture, required functionality, and jet and energy summation algorithm of the JEM. Various input test vector patterns were used to check the performance of the comlete energy summation algorithm. The test results using two JEM prototypes are presented and discussed. The subject of the second part is a Monte-Carlo study which determines the potential to measure the trilinear Higgs boson self coupling at the upgrade of the LHC, so called SuperLHC. The observation of HIggs boson pair production will be fundamental for a precise knowledge about the shape of the Higgs potential which is described b the trilinear and quartic Higgs boson self coupling. The sensitivity of the ATLAS experiment to measure the trilinear Higgs boson self coupling via the most promissing signal channel gg -> HH -> WWWW -> lvjjlvjj with two like-sign leptons in the final state has been studied in detail in an upgraded LHC scenario with an integrated luminosity of 6000 fb^(-1) for a Higgs boson mass range of 150 - 180 GeV/c^2. This study demonstrates that this task is quite challenging despite of the advantage of the SuperLHC.