Committee: Enectali Figueroa-Feliciano (Chair), Joseph Formaggio, and Lindley Winslow

Abstract
Cosmological and astrophysical evidence indicates that 85% of the matter content of the universe is in the form of non-baryonic dark matter. A large number of experiments are currently undertaking searches for weakly-interacting massive particles (WIMPs), the leading class of particle candidates for dark matter. We present the results of such a search with the SuperCDMS experiment, which uses Ge detectors cooled to 50mK to detect ionization and phonons produced by particle interactions. We perform a blind analysis of 577 kg d of exposure on 7 detectors targeting WIMPs with masses < 30 GeV, where anomalous results have been reported by previous experiments. No significant excess is observed and we set an upper limit on the spin-independent WIMP-nucleon cross section of 1.2 x 10^-42 cm^2 at 8 GeV. We also set constraints on dark matter interactions independent of the dark matter halo physics, as well as on annual modulation of a dark matter signal.

Cryogenic detectors similar to SuperCDMS also have potential applications in neutrino physics. We present several configurations in which dark matter detectors could be used with an intense neutrino source to detect an unmeasured Standard Model process called coherent neutrino scattering. This process may be useful, for example, as a calibration for next-generation dark matter detectors, and for constraining eV-scale sterile neutrinos. In addition, small cryogenic X-ray detectors on sounding rockets with large fields-of-view have the unique ability to constrain sterile neutrino dark matter. We set limits on sterile neutrino dark matter using an observation by the XQC instrument, and discuss prospects for future observations using the Micro-X instrument.