Leptophilic Dark Matter in Lepton Interactions at LEP and ILC

Abstract: Dark matter particles that couple primarily to leptons are only weakly constrained by data from direct detection experiments and the LHC. However, models of this kind necessarily generate effective four-lepton contact interactions at the tree- or one-loop-level, which can be probed in $e^+e^-$ collisions. In this work, precise data from LEP is used to derive limits on leptophilic dark matter in a model-independent framework. The bounds turn out to be competitive with, and in some cases exceed, limits from mono-photon events. We also extrapolate our results to ILC energies and luminosities. We show that ILC data for contact interactions may be able to set the strongest limits on TeV-scale leptophilic dark matter for couplings $g\gtrsim 1$ of the mediators.