 Weakly interacting massive particle

A weakly interacting massive particle is a massive dark-matter candidate whose interaction strength permits thermal production and later cosmological particle freeze-out. Its relic abundance depends on the annihilation rate and cosmological history, not on its mass alone. At nucleosynthesis temperatures a 50 GeV example is nonrelativistic: its equilibrium density is reduced by Boltzmann suppression, while an already frozen relic population need not follow the equilibrium density. Its effect on nucleosynthesis depends on whether the surviving energy density is appreciable or whether it injects reaction-altering products.

A Weakly Interacting Massive Particle (WIMP) is a hypothetical elementary particle that is a candidate for dark matter, which makes up a significant fraction of the universe's mass-energy content. WIMPs are predicted to have mass and interact primarily through the weak nuclear force and gravity, but not through electromagnetic interactions, which means they do not emit, absorb, or reflect light, making them difficult to detect directly.