Performance of the WASA detector for the HIBEAM experiment

Sammanfattning

The observed matter-antimatter asymmetry in the Universe suggests the existence of baryon number violating processes beyond what is present in the Standard Model of Particle Physics. The HIBEAM programme is a proposed experiment at the European Spallation Source (ESS) that investigates baryon-number violation through neutron-antineutron oscillations. Of specific interest to this work is the process $n \to \Bar{n}$, resulting in a violation of baryon number of two units, $\Delta \mathcal{B} = 2$. This thesis investigates the performance of the chosen detector setup, the WASA detector, with particular emphasis on the reconstruction of neutral and charged states. A \textsc{Geant4}-based simulation and a ROOT-based reconstruction framework are employed. The results show that the proposed detector system achieves high reconstruction efficiency for both charged and neutral states, with acceptance consistent with geometrical expectations. The employed particle identification scheme has been shown to provide high separation power among different charged particles. Finally, the developed event selection strategy is shown to achieve strong background suppression while maintaining high signal efficiency.