Probing freeze-in via invisible Higgs decay

In this work, we explore Higgs boson decays into dark matter (DM) within the context of the freeze-in mechanism under stronger coupling scenarios. Our analysis focuses on scalar DM candidates interacting through the Higgs portal, where the coupling strength can be significant without establishing thermal equilibrium, owing to a suppressed reheating temperature. We find that for DM masses as low as the MeV scale, the observed relic density can be reproduced while remaining consistent with existing collider and cosmological constraints. Notably, the framework predicts invisible Higgs decays at the level of a few percent, providing exciting prospects for experimental verification at the HL-LHC and FCC.