Probing ALP-portal Fermionic Dark Matter at the $e^+e^-$ Colliders

Axion-like particles (ALPs) are promising candidates for mediating interactions between a dark sector and the Standard Model (SM). In this work, considering the effective interactions of ALPs with the SM gauge bosons and a fermion dark matter (DM), we explore the DM relic satisfied parameter space and assess its testability through indirect searches. The potential of probing such ALP-portal fermionic DM at electron-positron colliders is investigated with the mono-photon + missing energy final states. We show that a spectacular distinction between the signal and SM background is possible via missing energy variable, the seed of which lies in the ALP-photon interaction, which also governs the relic density of DM. We further discuss the sensitivity of ALP-photon coupling using the $\chi^2$ analysis at the future electron-positron collider specifications.