Tim Tueschen ; Janis McKenna

2022
Universithy of British Columbia Vancouver, BC, Canada

Abstract: The so far unresolved question of the nature of dark matter has led to the development of a multitude of particle physics models that all meet current experimental and theoretical constraints, but differ greatly in the experimental signatures they predict. One idea that has been gaining popularity is that there could be a whole family of dark matter particles, forming a so called ’dark sector’ that interacts only very feebly with regular matter. In this thesis we investigate a hypothetical strongly interacting dark sector that confines at the GeV scale, which results in the production of a shower of dark sector mesons, including a long-lived neutral particle. This would result in a displaced vertex signature at e+e− colliders such as the Belle II experiment. We provide a brief overview of current evidence for Dark Matter and existing constraints to motivate the choice of a QCD–like dark sector with a dark photon mediator, as well as a detailed description of the Belle II detector which has an excellent sensitivity to displaced vertex signatures. After briefly summarizing the model, we describe the general search strategy, examine possible sources of background, and test the feasibility of a zero-background analysis. We find that, while not all signatures can be investigated in the zero-background case, the model offers a large parameter space that can be well investigated at Belle II with currently available data.

Note: Presented on 18 10 2022
Note: MSc