Exponentially Light Dark Matter from Coannihilation

Understand

Dark matter may be a thermal relic whose abundance is set by mutual annihilations among multiple species.

• Traditionally, this coannihilation scenario has been applied to weak scale dark matter that is highly degenerate with other states.
• We show that coannihilation among states with split masses points to dark matter that is exponentially lighter than the weak scale, down to the keV scale.
• We highlight the regime where dark matter does not participate in the annihilations that dilute its number density.