DEAP-3600 is the largest running dark matter detector filled with liquid argon, set at SNOLAB in Sudbury, Canada, 2 km underground. Since 2019 the experiment has held the most stringent exclusion limit in argon for Weakly Interacting Massive Particles (WIMPs) above 20 GeV/c². Such a result is a consequence of the large detector exposure and the extraordinary rejection power achievable in liquid argon against electron recoil backgrounds.

Besides WIMPs, noble liquid detectors can also be sensitive to super-massive dark matter candidates up to the Planck-scale. These dark matter candidates might have been produced non-thermally, like in inflaton decays mechanisms, or as radiation from primordial black holes, as well as extended thermal production in a dark sector. Specifically, dark matter candidates with masses above 10¹⁶ GeV and cross-sections in argon above 10^-24 cm² can also reach underground detectors like DEAP-3600. Their large cross-section results in a sequence of collinear nuclear recoils as they traverse the detector, resulting in a unique signal, different from the one expected from WIMPs or most of the backgrounds. This characteristic formed the basis of a dedicated analysis searching for heavy, multi-scattering dark matter.

The high quality of the selection cuts and the knowledge of the already modeled backgrounds allowed for the definition of four different Regions of Interest (ROIs), each with a background level of less than one event. After unblinding three years of data talking, no events were found in any of the ROIs, leading to world-leading constraints on two composite dark matter models up to Planck-scale masses.