Spinning the Higgs: Spin and parity measurement of the discovered Higgs-like boson in the H → WW → ℓνℓν decay mode

In this thesis, first the theoretical background of the Standard Model and the Higgs mechanism are described in chapter 1. Then the LHC and the ATLAS detector are presented in chapter 2. I have carried out several muon detector related tasks, of which being an expert-on-call for the muon detector system was the primary occupation, hence chapter 3 gives a concise overview of the Muon detector control and data acquisition systems. In chapter 4 the phenomenology, simulation and reconstruction of the events that are used in the analysis are explained. As said, the final state of the decay channel under study cannot be fully reconstructed. Nevertheless, we have developed a method to reconstruct events in the rest frame of the Higgs boson. At first the method was used to improve the Higgs mass resolution. However, after the discovery the method was optimised to allow for the construction of new spin and parity sensitive variables to be used in the properties analysis. This is the subject of chapter 5. Initially, in 2010, I started working on the rate measurement of the Higgs boson in the WW channel, both contributing to the analyses of the Higgs production through vector boson fusion and gluon gluon fusion. Since the discovery of the Higgs-like boson in 2012, I shifted to the spin and parity analysis, which is presented in two parts. Firstly, the preparations for the spin and parity measurement are described in chapter 6. Secondly, the actual measurement and results are presented in chapter 7. It is a fully analytical measurement, in the sense that the calculations at every step of the analysis can be evaluated. This distinguishes the analysis from the official ATLAS multivariate analysis. Finally, the conclusions and outlook are presented.