Materia oscura nella regione di risonanza dell'Higgs

Looking at the present universe, we realise the existence of an unknown form of matter, called dark matter, whose only traces come from its gravitational effects. The properties of dark matter are still unknown, but one possible way to explain it is to introduce an extension of the Standar Model. This thesis focuses on a specific portal model, where the interaction between dark matter and the Standar Model sector occurs through a mediator, which in our case is the Higgs boson. The aim of this study is to explore different scenarios by sequentially introducing a scalar field, a vector field or a fermionic field into the Standar Model Lagrangian. The first part of this work focused on the singlet scalar with Higgs portal case. We have calculated the cross sections required to solve the Boltzmann equation analytically for a candidate produced in the early Universe by the thermal freeze-out mechanism. We translated the analytical formulas into a code used to determine the relevant physical observables in this scenario, such as the relic density. In the second part of our study, we used various tools, including madDM and micrOMEGAs, to investigate and evaluate the bound of the parameters of the three different candidates. Our focus was primarily on utilising data obtained from direct experiments, with a particular interest in the LZ 2020 data, and from collider searches, such as ATLAS, to establish new constraints on these theories. We will see how the Higgs resonance region is not excluded by the experiment, and provide a candidate with the correct relic density.