UC Berkeley

Astrophysical evidence for dark matter is abundant; one of the great open problems in physics is its particle identity. In this dissertation we discuss two different detectors, LZ and HeRALD, designed to detect dark matter interactions. LZ is a recently assembled 10 tonne two-phase xenon time projection chamber. We discuss the first search for Weakly Interacting Massive Particles (WIMPs) from LZ, which set world-leading limits on the WIMP-nucleon interaction cross section. We present an extension of this search to lower masses via the Migdal effect, and suggest an alternative path for calculating the Migdal signal model for smaller recoil energies. We also show the design of a low energy photoneutron calibration source for LZ and data from its first deployment. The HeRALD detector is in active development, with R&D on different aspects of the superfluid helium-based design. We present an overview of this design and signal modeling work underlying projections of its sensitivity to low mass dark matter. We also discuss two experiments to probe this signal model by measuring helium scintillation from neutron and gamma ray interactions. Finally, we return to the photoneutron concept by presenting a source design that will serve as a path forward for even lower energy nuclear recoil calibrations important for further development of HeRALD.