Freeze-in of WIMP dark matter

Understand

The nature of dark matter (DM) remains one of the most important unanswered questions in particle physics.

• Here, we propose a novel scenario for DM in which weakly interacting massive particles (WIMPs) can freeze-in due to a first-order phase transition (FOPT) in the early Universe.
• The FOPT dilutes the pre-existing DM density to zero and leads to a sudden change in DM mass, preventing WIMPs from re-equilibrating due to their large mass-to-temperature ratio.
• Following the FOPT, WIMPs are produced via a freeze-in process, even though their interactions are NOT feeble.