WIMPs with GUTs: Dark Matter Coannihilation with a Lighter Species

Understand

We propose a new thermal freeze-out mechanism for ultra-heavy dark matter.

• Dark matter coannihilates with a lighter unstable species, leading to an annihilation rate that is exponentially enhanced relative to standard WIMPs.
• This scenario destabilizes any potential dark matter candidate.
• In order to remain consistent with astrophysical observations, our proposal necessitates very long-lived states, motivating striking phenomenology associated with the late decays of ultra-heavy dark matter, potentially as massive as the scale of grand unified theories, $M_\text{GUT} \sim 10^{16}$ GeV.