{
  "abstract": "We investigate the relativistic kinematics, spinor-recoil structure, and direct-detection phenomenology of a Dirac dark matter fermion interacting with SM charged leptons through a real scalar mediator within a low-energy effective Lagrangian in the fermion mass basis. Standard halo direct-detection searches lose sensitivity for sub-MeV dark matter, because the maximum recoil energy falls below detector thresholds. When halo dark matter particles are upscattered to relativistic energies by galactic cosmic-ray electrons (CRE), the momentum transfer in both the astrophysical upscattering stage and the terrestrial detection stage can exceed the fermion mass scales. By decomposing the tree-level $t$-channel cross section into three positive-definite contributions, we separate the static-numerator contribution from the linear and quadratic momentum-transfer spinor-recoil contributions, evaluated via convergent power series that reduce subtractive cancellation at small momentum transfer. For incident large kinetic energies, the spinor-recoil contributions become comparable to and begin to exceed $σ_0$; at substantially higher energies, they enhance the total cross section by several orders of magnitude relative to the static-numerator approximation. Furthermore, retaining the dynamical scalar propagator yields a high-energy cross section that decreases as $1/s$ and satisfies $s$-wave helicity partial-wave unitarity, in contrast to the linear $\\mathcal{O}(s/m_S^4)$ growth of the contact approximation. Applying the exact differential recoil spectra within an effective propagation model for cosmic-ray electron boosted dark matter (CRE-BDM), we derive $90\\%$ C.L. exclusion bounds in the 1 keV -- 10 MeV mass range from Super-Kamiokande, XENONnT, and PandaX-4T, extending experimental sensitivity into the sub-MeV window.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.36004",
  "author_total": 2,
  "authors": [
    {
      "name": "Nguyen Nhu Xuan"
    },
    {
      "name": "Vu Toan Thang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fjb5xg66e4mgm.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.36004",
  "fulltext_url": null,
  "id": "fjb5xg66e4mgm",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.36004",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "hep-ph"
    ],
    [
      "openalex",
      "3106|Dark Matter and Cosmic Phenomena"
    ]
  ],
  "openalex": "W7224109169",
  "pdf_url": "https://arxiv.org/pdf/2610.36004",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-26",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/fjb5xg66e4mgm.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:50Z",
      "native_id": "2610.36004",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.36004"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Relativistic Elastic Scattering of Cosmic-Ray Boosted Dirac Dark Matter with Charged Leptons through a Scalar Mediator",
  "title_text": "Relativistic Elastic Scattering of Cosmic-Ray Boosted Dirac Dark Matter with Charged Leptons through a Scalar Mediator",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:50Z",
  "url": "https://research.draconitic.com/paper/fjb5xg66e4mgm",
  "venue": "arXiv",
  "versions": []
}