Calorimétrie à argon liquide et recherche de nouvelle physique via l'étude de paires de quarks top boostés dans l'expérience ATLAS au LHC

The Standard Model of particle physics is a very predictive theory, but it still fails to explain some observations and so leads to the idea of the existence of new physics. To discover it experimentally, the ATLAS collaboration analyses the proton-proton collisions provided by the LHC. Analyses need data of good quality. Hence, the first part of this document describes a work to characterize the coherent noise bursts observed in the liquid argon calorimeters of the ATLAS experiment. Such noise has been studied and cured to ensure a high level of data quality. The second part of this thesis takes place in the context of a new physics search using top quark pairs. This study is focused on the case where boosted top quarks decay electronically. The reconstruction of top quarks in such cases was never optimized by the ATLAS collaboration. Therefore this study has lead to the definition and implementation of a new method called "electron-in-jet removal" improving significantly the top quark reconstruction in such topologies. This new method gives access to electrons that were previously removed. The correction factor applied to correct the imperfections of the simulation should then be computed for those electrons. Some preliminary measurements have been performed for the cases where the electron is within a jet. Two methods are presented as well as thoughts about future implementations.