Phenomenology of Higgs Bosons Beyond the Standard Model

Sammanfattning: After a long history of searches, a Higgs boson H was discovered by the ATLAS and the CMS experiments at the Large Hadron Collider (LHC) in 2012. Its properties fit well the ones predicted by the Standard Model (SM) of particle physics. However, the SM can not explain other established properties of Nature, such as the existence of Dark Matter. For this reason, models beyond the SM should be considered. Such models often predict the existence of several Higgs bosons and this thesis explores some of those models. In particular, the possibility to discover a charged Higgs boson, which would be a clear sign of physics beyond the SM, is studied.A commonly studied extension of the SM is the framework of two-Higgs-doublet models (2HDMs), where there are five Higgs bosons. By confronting the parameter spaces of some 2HDMs with publically available data from the LHC, the prospects for finding the 2HDM Higgs bosons is presented through the calculation of production cross sections and decay branching ratios in various channels.A new kind of 2HDM, called the Stealth Doublet Model is presented and the properties of the Higgs bosons are studied. In this model, it is shown that in particular the properties of the charged Higgs boson H± have new features not exhibited in earlier studied models. Within the parameter space compatible with the LHC results, the production cross section for H± can be sizeable enough to be experimentally observed.Finally, the discovery prospects at the LHC, for a H± in the pp → tH± process, with the decays H± → HW± and H → bb, is studied in various models beyond the Standard Model. It is shown that for the supersymmetric models, this channel is beyond the discovery reach of the LHC. In some of the other studied models, in particular the Aligned 2HDM, the situation is improved and the channel is feasible.