The existence of this “dark matter” is consistent with evidence from large-scale galaxy surveys and cosmic microwave background measurements, which indicate that the majority of matter in the universe is non-baryonic. The nature of this non-baryonic component is still totally unknown, and the resolution of the “dark matter puzzle” is of fundamental importance to cosmology, astrophysics, and elementary particle physics.

One leading explanation, motivated by supersymmetry theory, is that dark matter is comprised of as-yet-undiscovered Weakly Interacting Massive Particles (WIMPs) formed in the early universe and subsequently gravitationally clustered in association with baryonic matter.

In principle, WIMPs could be detected in terrestrial experiments through their collisions with ordinary nuclei, giving observable low-energy (<100 keV) nuclear recoils. The predicted collision rates are extremely small and require ultra-low background detectors with large (1–100 ton) target masses, located in deep underground sites to eliminate neutron background coming from cosmic ray muons.

The goal of DarkSide-20k is ultimately to try and detect particle-like dark matter. But what if it could also detect neutrinos? Neutrinos are the lightest particles with the smallest mass of all the elementary particles within the Standard Model, so light that they were believed to be massless until about twenty years ago.