Weakly Interacting Massive Particles (wimps)

Broad class of particles that were once in thermal equilibrium with the early universe but were "cold," i.e., moving non-relativistically at the time of structure formation. WIMPs have nonzero rest mass and participate only in the weak nuclear interaction. WIMPs are expected to have collapsed into a roughly isothermal, spherical halo within which the visible portion of our galaxy resides, consistent with measurements of spiral
galaxy rotation curves. The original WIMP was a heavy Dirac neutrino, now experimentally ruled out. The neutralino predicted by supersymmetric extensions of the Standard Model is the favorite WIMP nowadays. Such particles could fill space and provide gravitational force without any associated luminosity. As such they are a candidate for dark matter. Another candidate WIMP is the axion. Direct detection of WIMPs is possible through their elastic scattering from nuclei. However, contributions of individual nucleons summed coherently yield extremely small WIMP-nucleus cross sections.