Whats the difference between a neutrino and a neutralino?
Neither has an electric charge, and each probably makes up some of the missing matter but otherwise they have little in common. The neutrino carries almost no mass. It moves at nearly the speed of light, which makes it “hot dark matter.” This velocity means that it could not have made galaxies congeal in the early universe. Most neutrinos remain from the beginning of the universe, but particle decay and atomic fusion in stars continue to produce them. Supersymmetry predicts the existence of the massive neutralino. We know it carries at least 46 times the mass of a proton because otherwise experiments at the Large Electron-Positron collider (LEP) at CERN would have detected their production. If it is a WIMP, it travels through the universe at 1/1000 the speed of light, making it “cold dark matter.” Neutralinos were produced at the beginning of the universe but exist in fewer numbers than the neutrino because their great mass makes them harder to produce, and they annihilate each other.
