FIPs

Feebly interacting particles (FIPs) are subatomic particles defined by having extremely suppressed interactions with the Standard Model (SM) bosons and / or fermions. These particles are potential thermal dark matter candidates, extending the model of weakly interacting massive particles (WIMPs) to include weakly interacting sub-eV particles (WISPs) and others. FIP physics is also known as dark-sector physics.

For more information, see Wikipedia.