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  • Open Access

Hitting the Thermal Target for Leptophilic Dark Matter at Future Lepton Colliders

Cari Cesarotti1,* and Gordan Krnjaic2,3,4,†

  • *Contact author: c.cesarotti@cern.ch
  • †Contact author: krnjaicg@fnal.gov
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Phys. Rev. Lett. 135, 171802 – Published 22 October, 2025

DOI: https://doi.org/10.1103/w1bw-w7wt

Abstract

We study future lepton collider prospects for testing predictive models of leptophilic dark matter (DM) candidates with a thermal origin. We calculate experimental milestones for testing the parameter space compatible with freeze-out and the associated collider signals at past, present, and future facilities. This analysis places new limits on such models by leveraging the utility of lepton colliders. At e+e− machines, we make projections using precision Z-pole observables from e+e−→ℓ+ℓ−+E signatures at large electron-positron collider and future projections for future circular collider (ee) in these channels. Additionally, a muon collider could also probe new thermal relic parameter space in this scenario via μ+μ−→X+E, where X is any easily identifiable standard model object. Collectively, these processes can probe much of the parameter space for which DM direct annihilation to ℓ+ℓ− yields the observed relic density in Higgs-like models with mass-proportional couplings to charged leptons.

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Phys. Rev. Lett. 135, 171802– Published 22 October, 2025
  • Received 12 November 2024
  • Revised 14 July 2025
  • Accepted 18 September 2025
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