Phenomenological aspects of 'Beyond the Standard Model' theories at the LHC

• Main Author: Schaefers, Patrick Bernhard
• Other Authors: Belyaev, Alexander
• Published: University of Southampton 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.741729

In this thesis, we study the phenomenological implications of different Beyond the Standard Model (BSM) theories at the Large Hadron Collider (LHC) with a focus on the anomalous magnetic moment of the muon Δa_μ and dark matter (DM). We consider two Grand Unified Theory (GUT) scale models, namely a Pati-Salam model with A₄×Z₅ family symmetry as well as an SU(5) with A₄ family symmetry. After both models break down to the Minimal Supersymmetric Standard Model (MSSM), we study their capabilities of explaining Δa_μ, DM and further collider and non-collider constraints. We find that both models comprise a viable set of parameters leading to distinctive solutions, provided the gaugino masses are non-universal. We also explore the capability of models with extra vector resonances Z' to account for DM when combined with a coloured vector-like top partner sector. We find that the presence of a Z' boson may greatly improve the sensibility of the LHC to such models, especially in regions where non-collider searches are considerably less sensitive. Finally, we study the potential of current and future hadron colliders to narrow down the nature of the 2012 discovered scalar particle at the LHC, which matches the Standard Model (SM) Higgs boson astonishingly well so far. To further determine whether this scalar may belong to a different BSM theory, we use an effective field theory to study the unitarity violations arising from Higgs couplings to vector bosons slightly different as compared to the SM. We find that triple Higgs production substantially benefits from non-SM couplings and can be probed effectively at a 100 TeV future collider with high precision.