DIRECT SEARCHES FOR PARTICLE DARK MATTER

The search for the particle which constitutes more than 90% of the mass of the universe has eliminated or severely restricted many candidates. While accelerator-produced results and indirect searches have helped, the most extensive exclusion of heavy candidates has come from attempts at direct detection using semiconductor ionization detectors. The exclusion by direct detection extends over 12 orders of magnitude in particle mass and 20 orders of magnitude in cross section for Dirac particles. Light neutrinos, while not detectable directly, can be eliminated as dominant dark matter, if the 17-keV neutrino exists, although they could still constitute a part of dark matter. The search for the dominant cold dark matter must now get to cross sections less than one-tenth that of the weak interaction for Dirac masses > 20 GeV and utilize detector nuclei with spin for Majorana masses greater than or similar to 10 GeV. A program to achieve these goals is being implemented with a cryogenic detector.