LHC friendly avenues for freeze-in dark matter

Freeze-in dark matter (DM) production constitutes an appealing mechanism to generate the DM relic density for very weakly coupled DM particles which never achieve thermal equilibrium with the Standard Model (SM). We examine the collider probes of freeze-in DM through the decay of parent particles and highlight the complementarity of ATLAS/CMS and the planned MATHUSLA detector in probing such freeze-in DM scenarios at the LHC.