Characterization of the DarkLight trigger system

Despite the long-standing success of the Standard Model, we know it to be an incomplete description of our universe as it does not describe dark matter: a sector of matter discovered through cosmological observations of its large-scale gravitational interactions. The particle scale interactions of dark matter remain unknown. A dominant open question in particle physics is how dark matter interacts with itself and how (if at all) dark matter interacts with Standard Model particles. DarkLight seeks to address this question through the search for a dark boson: a postulated particle that would mediate interactions between the Standard Model and dark matter. DarkLight will attempt to produce the dark boson using the TRIUMF superconducting electron linear accelerator, and identify the dark boson through the reconstruction of its mass using its Standard Model decay products. Parent particle mass reconstruction relies on the correct identification of particles as originating from the same decay. This manifests as particles arriving at the detector system at the same time. To make this identification, a trigger system is used to make precise measurements of the arrival times of particles and prompt data readout when a coincidence is observed between each particle type’s detector system. A thorough understanding of the capabilities and limitations of the trigger system is necessary to ensure this identification is correct and to maintain data quality. This thesis presents the characterization of the DarkLight trigger system. The time resolution of the system is found to exceed the minimum standard for confident decay pair matching, and the trigger system is determined to be able to resolve the position of impact of an incoming particle, which is an important feature in background suppression. A discussion of the accuracy of time measurements made using the trigger system is presented. The efficiency of the trigger detectors is maintained across their central region, but further investigations into the peak efficiency are required. The system was found to be minimally affected by scintillator crazing. While poor light guide connections have a significant negative impact on data quality, they can be identified for replacement from the analysis of pulse width data.