Adopting a model independent approach, we constrain the various effective interactions of leptophilic DM particles with the visible world from the WMAP and Planck data. The thermally averaged indirect DM annihilation cross section and the DM-electron direct-detection cross section for such a DM candidate are observed to be consistent with the respective experimental data. We study the production of cosmologically allowed leptophilic DM in association with Z (Z → ff ), f ≡ q, e − , μ − at the ILC. We perform the χ 2 analysis and compute the 99% C.L. acceptance contours in the m χ and Λ plane from the two-dimensional differential distributions of various kinematic observables obtained after employing parton showering and hadronisation to the simulated data. We observe that the dominant hadronic channel provides the best kinematic reach of 2.62 TeV (m χ = 25 GeV), which further improves to ∼3 TeV for polarised beams at √ s = 1 TeV and an integrated luminosity of 1 ab −1 .

We explore the viability of detecting a leptophilic scalar dark matter at the ILC in a model-independent way. We present the constraints on the couplings of scalar dark matter with the standard model fermions ensuing from the relic density bounds deduced from the 2018 Planck data. We, then, present the reach of the ILC in terms of Λ, the scale of the effective theory, by performing a detailed analysis for the Z associated DM pair production (i.e., e + e − → 2 jets + E T , e + e − → µ + µ − + E T and e + e − → e + e − + E T ). We present the results for various run scenarios as 3-σ contours in the m φ − Λ plane. We also analyse the effect of beam polarization on the sensitivity of this search. We find that for the process with two hadronic jets in the final state, ILC can probe Λ up to 3.1 TeV for √ s = 1 TeV that can further enhance to 3.95 TeV, after the inclusion of polarization effects.