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In this thesis we use the Effective Field Theory approach for supersymmetric theories, applied to two experimental domains : the search for the Higgs bosons at colliders and the Dark Matter observables. The reason for introducing an effective approach in the Higgs physics is that the simple supersymmetric extension of the Standard Model (the MSSM) is known to have a tightly constrained Higgs sector, in particular with a lightest Higgs mass difficult to raise without introducing some fine-tuning. Many specific expansions (as the NMSSM for instance) allow for a richer Higgs sector. In this case however, the effective approach is handy since it encompasses many different specific ultraviolet completions. We have added to the Kahler and superpotential of the MSSM all possible terms of dimensions 5 and 6 including only Higgs superfields. The phenomenology of the resulting Higgs sector appears to be much richer, and we analyse our model in view of the latest LHC results. On the other side, supersymmetry is known for providing a Dark Matter candidate, so we have also worked to improve the accuracy of the computation of the relic density in the MSSM. Indeed the impressive accuracy on the experimental side (around 6%) calls for a precise computation including radiative corrections. Those one-loop computations being rather long in the MSSM, thus often overlooked, we have used again the effective approach by introducing new effective vertices that aim at accounting for the one-loop correction. We show on a specific process (neutralinos annihilation to muons) the agreement between the effective approach and the full one-loop computation.
Supersymmetric (SUSY) extension of the Standard Model (SM) is a primary candidate for new physics beyond the SM. If SUSY breaking scale is very low, for example, the multi-TeV range, and the SUSY breaking sector, except for the goldstino (gravitino),
Predictions for the Higgs masses are a distinctive feature of supersymmetric extensions of the Standard Model, where they play a crucial role in constraining the parameter space. The discovery of a Higgs boson and the remarkably precise measurement o
We compute the two-loop QCD corrections to the neutral Higgs-boson masses in the MSSM, including the effect of non-vanishing external momenta in the self-energies. We obtain corrections of O(alpha_t*alpha_s) and O(alpha*alpha_s), i.e., all two-loop c
The recent results from the ATLAS and CMS collaborations show that the allowed range for a Standard Model Higgs boson is now restricted to a very thin region. Although those limits are presented exclusively in the framework of the SM, the searches th
Spurred by the discovery of a boson resonance at the LHC as the result of the search for the Standard Model Higgs, we pursue our investigation of the properties and signatures of Higgses in an effective supersymmetric scenario that goes beyond the us