Colloquium- Scott Haselschwardt (Berkeley Lab)- Searching high and low for dark matter with liquid noble detectors

Abstract: Understanding the particle nature of dark matter is one of the most pressing tasks of modern science, motivating numerous theoretical dark matter candidates and experimental efforts to detect them. Chief among these are direct-detection experiments which use liquified noble gasses as their detection medium. 

In this talk I will describe direct searches for weak-scale dark matter particles, highlighting the most sensitive experiment of this type to date: the LUX-ZEPLIN (LZ) experiment, which uses liquid xenon as its detection medium. I will then discuss future efforts aimed at detecting dark matter lighter than the proton. These include an LZ upgrade to dissolve hydrogen in its target volume (HydroX) and the development of a low-threshold detector based on quasiparticle excitations of a superfluid helium-4 target (HeRALD). Taken together, these experiments directly probe an extremely well-motivated class of models known as “thermal relics”: dark matter particles that were once in thermal equilibrium with ordinary matter in the early Universe.