Exotic Dark Matter Search with the MAJORANA DEMONSTRATOR

With excellent energy resolution and ultralow-level radiogenic backgrounds, the high-purity germanium detectors in the MAJORANA DEMONSTRATOR enable searches for several classes of exotic dark matter (DM) models. In this work, we report new experimental limits on keV-scale sterile neutrino DM via the transition magnetic moment from conversion to active neutrinos vs -> va. We report new limits on fermionic dark matter absorption (x +A -> v+ A) and sub-GeV DM-nucleus 3 -> 2 scattering (x + x + A -> phi + A), and new exclusion limits for bosonic dark matter (axionlike particles and dark photons). These searches utilize the (1-100)-keV low-energy region of a 37.5 -kg y exposure collected by the DEMONSTRATOR between May 2016 and November 2019 using a set of 76Ge-enriched detectors whose surface exposure time was carefully controlled, resulting in extremely low levels of cosmogenic activation.