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  • Open Access

New thermal-relic targets for sub-GeV dark matter direct detection

Xu Han1,* and Gordan Krnjaic2,3,4,†

  • *Contact author: xuhan7@uchicago.edu
  • †Contact author: krnjaicg@uchicago.edu
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Phys. Rev. D 114, 016024 – Published 22 July, 2026

DOI: https://doi.org/10.1103/hgk4-zspm

Abstract

Dark matter direct detection experiments involving electron recoils are beginning to test highly predictive, thermal-relic milestones for sub-GeV dark matter models. Due to the Lee-Weinberg bound, thermal dark matter candidates in this mass range necessarily require comparably light mediator particles to achieve a suitably large annihilation cross section. Here we present new thermal-relic milestones for sub-GeV dark matter candidates that couple to vector mediators. In these models, the mediators are massive gauge bosons of anomaly-free Abelian extensions to the Standard Model, including the dark photon, gauged Li−Lj,B−L, and B−3Li models, where B is the baryon number, L is the lepton number, and i, j index the lepton families. Since the same interactions that govern cosmological production also govern electron scattering, the targets we present are firmly predictive and allow for these models to be robustly discovered or falsified. Furthermore, since the mediators we study exhaust the minimal anomaly-free U(1) extensions to the Standard Model, our results offer a complete list of predictive milestones for sub-GeV dark matter coupled to vector mediators.

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Phys. Rev. D 114, 016024– Published 22 July, 2026
  • Received 11 March 2026
  • Accepted 1 July 2026
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