DOE OSTI2018
Overwhelming evidence from astrophysical observations indicates that only 20% of the matter in the universe consists of ordinary matter, while the remaining 80% is made of some form of matter called "dark matter''. Although these indirect astrophysical observations convince us that dark matter exists, dark matter has not yet been directly observed. The standard model of particle physics, which has been very successful in explaining the properties of ordinary matter, can neither explain dark matter's presence nor its properties. The discovery and identification of dark matter would have a profound impact on cosmology, astronomy, and particle physics. A leading dark matter candidate consistent with all astrophysical data is a weakly interacting massive particle (WIMP). WIMPs could be detected through their interactions with atomic nuclei in specially designed detectors. Since the collision rates are expected to be very small (a few collisions per year for a 1-ton detector), large detectors with low backgrounds and excellent detection capability for rare collisions are needed to gain knowledge of the nature of dark matter. With dark matter experiments such as the LZ experiment, we are in a position to detect and study this dark matter through sensitive terrestrial direct detection experiments. If no discovery is made with LZ, it will be very difficult to reconcile the sensitivity limit of this experiment with most conventional WIMP scenarios, and alternate paradigms will have to be strongly considered for dark matter. The main focus of the U-M dark matter group over the past two years was on design validation and fabrication for the LZ project, followed by commissioning and operation of the LZ dark matter experiment, and the analysis of the science data during the following funding cycle. The U-M dark matter group had identified two key areas to contribute to the LZ project: the design and fabrication of a radon removal element for the xenon circulation system, and the execution and coordination of prototyping and design validation performed by the small xenon chamber group.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗