Search for the Standard Model Higgs Boson in the $H->ZZ->l^{+}l^{-}q\overline{-}q$ Decay Channel at CMS

The theoretical foundations of the Standard Model of elementary particles relies on the existence of the Higgs boson, a particle which has been revealed for the first time by the experiments run at the Large Hadron Collader (LHC) in 2012. The discovery of a Higgs boson depended on its decay products, as it is an unstable particle. In this thesis the author has conducted a search for the Higgs boson in the H → ZZ → l +l - qq Decay Channel at CMS with 4.6 fb−1 of data collected by the Compact Muon Experiment. The presence of jets in the final state poses a series of challenges to the experimenter: both from a technical point of view, as jets are complex objects and necessitate of ad-hoc reconstruction techniques, and from an analytical one, as backgrounds with jets are copious at hadron colliders, therefore analyses must obtain high degrees of background rejection in order to achieve competitive sensitivity. The main tool of background discrimination is provided by an angular likelihood discriminant, capable of selecting events likely to originate from the decay of a scalar boson, and discriminate non-resonant backgrounds. The events passing the selection requirements in 4.6 fb−1 of data collected by the CMS detector are examined, in the search of a possible signal compatible with the decay of a heavy Higgs boson, the modeling of which is shown in detail. The statistical tools which are adopted to perform such an analysis are described, and the results are provided. This thesis is a paradigm for studies of the Higgs boson with final states with jets. The non-expert physicists will enjoy a complete and eminently readable description of a proton-proton collider analysis. At the same time, the expert reader will learn the details of the searches done with jets at CMS.