Dylan Temples (Northwestern University) New Directions in Liquid Noble Dark Matter Searches: Probing the Sub-GeV Regime

Abstract: 

The most sensitive searches for dark matter (DM) with mass above ~10 GeV/c2 use the dual-phase xenon time-projection chamber (LXe-TPC) technology. In the U.S., development of this technology is spearheaded by the LUX-ZEPLIN experiment, with first science data coming soon. As these detectors increase in scale and sensitivity, previously negligible backgrounds become important to understand, both to prevent false discovery claims and to accurately measure the ultimate DM sensitivity of such an experiment. In this talk, I will discuss one class of such backgrounds: neutrinos scattering from the inner-shell electrons of a xenon atom. This process has heretofore gone uncalibrated, and due to its distinct event topology, is more akin to a nuclear recoil (potential DM signal) than an electron recoil (background). I will also discuss two liquid-noble technologies for searching for dark matter below ~5 GeV/c2: light-element doping, and superfluid helium detectors. Doping an LXe-TPC with low concentrations of light elements, such as hydrogen, enables sensitivity to dark matter models with mass down to 20 MeV/c2 while simultaneously probing spin-dependent DM-nucleon coupling. Superfluid helium detectors offer a complementary DM search avenue, as it is more sensitive to low-mass spin-independent DM than hydrogen-doping, but cannot investigate spin-dependent coupling.