Recherche du boson de Higgs chargé dans le canal H+ -> tb et étiquetage des jets b avec l'expérience ATLAS auprès du LHC.

The only particle of the Standard Model that has not yet been discovered is the Higgs boson, which explains the origin of the masses of elementary particles. In the Minimal Supersymmetric extention to the Standard Model (MSSM), the Higgs sector consists of five bosons, two of which are charged. The search for a charged Higgs boson in the gg ¯tbH+(H+ ! t¯b) channel, is the main topic of this analysis. We present an analysis that uses a likelihood function to resolve combinatorics while reconstructing the charged Higgs boson, and the b-tagging to suppress the t¯t+jets background. We also present the difficulties due to the combinatoric background reducing the discovery potential of this channel. The presence of 4 b quarks in the final state that we are looking at, makes the b-tagging an important tool for the analysis. Therefore, a part of this work is dedicated to the study of b-tagging. We present in the context of the preperation for the first data, several studies dedicated to the optimisation and the understanding of the b-taggingperformance. We also present the commissioning of a simple tagger (JetProb) to be used with first data analysis.