[en] In this report for an Accreditation to Supervise Researches (HDR), the author briefly presents works performed within the ATLAS experiment and proposes an overview of his works in relationship to the different phases of the LHC programme: starting the detector and data preparation (the electromagnetic calorimeter), analysis of data from Run 1 with the discovery of the Higgs boson), and preparation of upgrades for the high luminosity phase of the LHC. The report is completed by six published articles: Monitoring and data quality assessment of the ATLAS liquid argon calorimeter; readiness of the ATLAS liquid argon calorimeter for LHC collision; measurement of the isolated diphoton cross-section in pp collisions with the ATLAS detector; Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC; Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC; Search for scalar diphoton resonances with the ATLAS detector