Direct Detection of sub-GeV Dark Matter: A New Frontier

Rouven Essig
C. N. Yang Institute for Theoretical Physics
Stony Brook University, New York, USA

Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity. While large experiments are focusing on the search for Weakly Interacting Massive Particles (WIMPs) with masses above the proton (about 1 GeV/c^2), many natural dark-matter candidates have masses below the proton and are invisible in traditional WIMP searches.

In this talk, I will discuss how small-scale experiments can search for dark matter with masses between about 500 keV/c^2 to 1 GeV/c^2 (“sub-GeV dark matter”). I will describe several direct-detection strategies, focusing on searches for dark matter interactions with electrons and nuclei in various target materials, such as noble liquids and semiconductors. There has been tremendous progress in probing sub-GeV dark matter in the last few years, which relies on the exciting interplay between various subfields of physics, including particle physics theory and experiment, cosmology, astrophysics, condensed matter physics, quantum sensing, and instrumentation. I will in particular also highlight the SENSEI experiment, which uses ultra-low-threshold silicon CCD detectors (“Skipper CCDs”) capable of detecting even single electrons.