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 effect of early kinetic decoupling is also discussed in the resonant regime. The potential of probing such ALP-portal fermionic DM at the electron-positron colliders is investigated with the mono-photon plus missing energy final states. We show that a spectacular distinction between the signal and SM background is possible via the 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.