PNNL

Abstract

With excellent energy resolution and ultra-low level radiogenic backgrounds, the high-purity germanium (HPGe) detectors in the Majorana Demonstrator enable searches for several classes of exotic dark matter (DM) models. In this work we report the first experimental limits on the fermionic dark matter absorption process (? + T ? ? + T) and sub-GeV DM-nucleus 3?2 scattering (? + ? +T ? f+T), new exclusion limits for bosonic dark matter (axionlike particles and dark photons) and keV-scale sterile neutrino DM via the transition magnetic moment (TMM) of conversion to active neutrinos, ? s ? ? a. These searches for exotic DM utilize the 1–100 keV low energy region of a 37.8 kg-y exposure collected by the Demonstrator between May 2016 and Nov. 2019, using a set of 76Ge-enriched detectors whose surface exposure time was carefully controlled, resulting 8 in extremely low levels of cosmogenic activation.