Interplay of super-WIMP and freeze-in production of dark matter

Nonthermalized dark matter is a cosmologically valid alternative to the paradigm of weakly interacting massive particles. For dark matter belonging to a Z2-odd sector that contains in addition a thermalized mediator particle, dark matter production proceeds, in general, via both the freeze-in and super-WIMP mechanism. We highlight their interplay and emphasize the connection to long-lived particles at colliders. For the explicit example of a colored t-channel mediator model we map out the entire accessible parameter space, cornered by bounds from the LHC, big bang nucleosynthesis and Lyman-α forest observations, respectively. We discuss prospects for the HL- and HE-LHC.