Dark Matter

Fermilab holometer prototype cavity
Astronomical and cosmological observations lead to the conclusion that our galaxy is embedded in a halo of cold dark matter. The composition of this dark matter is unknown, and its existence shows that the Standard Model of particle physics is incomplete. Several theories of particle physics, such as Supersymmetry, predict the existence of Weakly Interacting Massive Particles (WIMPs) with properties suitable for explaining the dark matter. The goal of the FCPA experimental program is to directly detect WIMPs in our halo by measuring nuclear recoils from WIMP-nucleus interactions.

The expected rate of WIMP interactions is already constrained to be very small (less than one event per kg-year) and the expected nuclear recoil energy is very low (100 keV or less) so background rejection is crucial. One requirement is the ability to distinguish nuclear recoils from electron recoils arising either from beta decays or compton scattering of gamma rays. Another requirement is to eliminate neutron backgrounds, since neutrons produce nuclear recoils identical to those from WIMP interactions. To eliminate the fast neutron flux induced by cosmic rays, such experiments must be located deep underground.

We are pursuing three experiments to search for dark matter: