Dylan Harries: Naturalness, Dark Matter and E6 Inspired SUSY Models

The unknown nature of dark matter and other unsolved problems point to the need for Beyond the Standard Model physics. Supersymmetric models are among the most highly motivated extensions of the Standard Model. However, the results of extensive searches for new physics suggest that many preferred scenarios predicted in the minimal supersymmetric standard model (MSSM) are not realised. The fact that these pre-LHC expectations, which were commonly guided by ideas about naturalness, have gone unmet raises the question as to whether the MSSM is fine-tuned. This possibility is one of the motivations for studying non-minimal supersymmetric models. In this talk, we will explore several extensions of the MSSM that can arise from an underlying E6 gauge symmetry. We first discuss the general problem of quantifying fine-tuning, relating traditional measures to a rigorous approach based on Bayesian statistics. We then investigate a new source of fine-tuning in the simplest E6 inspired models, associated with the presence of a massive Z' boson. Finally, we study potential dark matter candidates in one recently proposed model, with a focus on the implications of current and future direct detection searches.