Early kinetic decoupling and a pseudo-Nambu-Goldstone dark matter model

Understand

We study the early kinetic decoupling effect in a pseudo-Nambu-Goldstone (pNG) dark matter (DM) model.

• The pNG DM scattering processes with particles in the thermal bath in the early Universe are suppressed by the small momentum transfer.
• As a result, kinetic equilibrium is not maintained, and the temperature of DM is different from the temperature of the thermal bath at the freeze-out era.
• This temperature difference affects the thermal relic abundance of DM.