Search for supersymmetric particles in the jets channel and missing energy in the ATLAS detector

The main issue of this work is the search for supersymmetric particles with the ATLAS detector at the LHC (Large Hadron Collider). The first chapter focuses on the phenomenological aspect of supersymmetry and on the experimental constraints to discover it at Tevatron or LHC accelerators. The author has focused his work to look for squarks and gluinos in the specific frame of the mSUGRA model at the LHC with the ATLAS detector. The second chapter presents the LHC and the ATLAS detector with its various components: semiconductor tracker (SCT), transition radiation tracker (TRT), calorimeters and muon spectrometer. The signature of supersymmetry that is looked for in this work is based on jets and missing energy, both quantities are deduced from the data delivered by the calorimeters. The third chapter is dedicated to ATLAS calorimetry, the understanding of its signals and the identification of its background noise. The fourth chapter presents the data analysis for the search for squarks and gluinos in the final decay state defined by jets + transverse missing energy without leptons. With 200 pb-1 of data no excess in the 0-lepton channel has been yet detected. The last chapter presents the most recent results of ATLAS and CMS concerning the search for supersymmetric particles in the frame of mSUGRA: the search has been enlarged to 1-lepton and 0-lepton+b-jets channels