Strong evidence suggests that the dominant mass in the universe is in the form of “dark matter”: effectively cold, nearly non-interacting particles. So far, the measured effects of these particles are caused by their gravity. Fermilab experiments test the hypothesis that these particles are a new form of matter, a relic from the hot early stages of the big bang.
Fermilab leads a direct experimental search for weakly interacting massive particles (WIMPs). These experiments, deployed deep underground to shield from cosmic ray backgrounds, seek recoils of atomic nuclei from extremely rare collisions of dark matter particles. The range of most plausible theoretical models will be explored in the next few years.
The mass and detailed interactions of these particles are not known. Fermilab’s program employs a range of target materials and detection technologies to study a wide range of particle types. These include the Cryogenic Dark Matter Search (CDMS) experiment, which uses germanium and silicon detectors cooled to very low temperatures at the Soudan mine in northern Minnesota; the PICASSO-COUPP (PICO) experiment, using bubble chambers located at SNOLAB (Ontario, Canada) to detect recoiling nuclei; and the Darkside experiment, which employs liquid argon as the detection material in the Gran Sasso laboratory in Italy.
Next-Generation Dark Matter
We are currently wrapping up Generation 1 (G1) and constructing Generation (G2) dark matter experiments. Fermilab is also actively thinking about future generation (G3 and beyond) dark matter experiments. These include WIMP dark matter experiments that can explore down to the neutrino “floor”, axion experiments that will extend sensitivity up to masses of 10^e3 eV and other searches for exotic dark matter that will extend parameter space by an order of magnitude or more. Please follow this link to learn about our discussion group, which is open to all researchers in the Chicago area (services account and password required).