Status of direct searches for WIMP dark matter

Astrophysical observations indicate that about 23% of the energy density of the universe is in the form of non-baryonic particles beyond the standard model of particle physics. One exciting and well motivated candidate is the lightest supersymmetric partner particle (LSP), which could be a weakly interacting massive particle (WIMP) left over from the Big Bang. To determine that the LSP is the dark matter, it is necessary both to measure the particle's properties at an accelerator and to detect the particle in the galaxy directly (or indirectly). Direct detection of these particles requires sophisticated detectors to defeat much higher-rate backgrounds due to radioactivity and other sources. Promising techniques identify individual interactions in shielded fiducial volumes and distinguish nuclear-recoil signal events from electron-recoil backgrounds, based on the timing, energy density, and/or the division of the energy into signals of ionization, scintillation, or phonons. I review the techniques of the dozens of experiments searching for WIMPs and summarize the most interesting results and prospects for detection.