The PICO Dark Matter Search: Reflections and Projections
dark matter , direct detection , discovery limit , neutrino , neutrino floor , neutrino backgrounds , profile likelihood , annual modulation , retroreflectivity , retroreflector , bubble chamber , nuclear recoil , ray tracing , weakly interacting massive particle , WIMP , coherent neutrino scattering , CEvNS
Dark matter remains one of the most intriguing mysteries of modern physics, and has sparked numerous experimental efforts to uncover its particle nature. Direct detection experiments using low threshold detectors in clean, underground environments to look for nuclear recoils have proved to be an effective way to search for particle dark matter. The PICO experiment is one such effort, operating bubble chambers with fluorocarbon targets and offering unique sensitivity to spin dependent dark matter scattering. This thesis describes the motivation behind PICO and then presents a new retroreflector design for PICO-40L, the most recent PICO detector. The new design gives improved optical coverage in the detector with fewer radioactive contaminants than in PICO-60, the previous detector. The physics reach of future detectors is then explored, with particular focus on the sensitivity to coherent neutrino scattering and annual modulations within a dark matter signal. A new neutrino floor is calculated using timing information, and the sensitivity to annual modulations of a dark matter signal in the future PICO-500 detector is quantified.