Dark Matter Annihilation is the matter/Antimatter Annihilation of WIMPs, Dark Matter Particles. A favorable WIMP candidate, the Neutralino, is its own Antiparticle, and an interaction between two will annihilate as would an electron and positron. Given the lack of much of a force bringing them together (only Gravity, which is quite weak at particle scale), the amount of annihilation is not enough to make much mass difference after the time of the very Early Universe. Details of such annihilation, such as the relevant Cross Section are part of theories of Big Bang Nucleosynthesis and the resulting particle Abundances. Such annihilation may produce Photons, but also other particles, and detection of some possible results has been proposed as a means to help confirm dark matter's existence.