{
  "abstract": "We study freeze-in production and experimental probes of inelastic dark matter (iDM) coupled to the Standard Model through dimension-6 transition anapole and charge-radius operators. These interactions arise upon integrating out the heavy dark photon of a broken $U(1)_D$ vector portal. We focus on mass splittings below the dielectron threshold, where the excited-state decay is cosmologically long-lived and decays predominantly through $χ_1\\toχ_0+3γ$, producing a distinctive keV--MeV photon spectrum. We calculate the decay rate and photon spectrum analytically in the Euler--Heisenberg limit and evaluate finite-electron-mass corrections using the full one-loop amplitude. We then combine X-ray limits with freeze-in relic density targets and complementary direct detection (DD) and accelerator constraints. The surviving $χ_1$ population also leads to exothermic downscattering signatures at DD experiments, including the possibility of explaining the LZ signal, while the three-photon decay is constrained by X-ray data. At $Δ=900\\,\\mathrm{keV}$, INTEGRAL/SPI probes the Boltzmann-suppressed high-mass branches of the freeze-in targets, whereas the NuSTAR limits at $Δ=100\\,\\mathrm{keV}$ are substantially weaker because of the steep splitting dependence of the decay width. Our results demonstrate the potential of X-ray observations as a probe of freeze-in through a decoupled vector portal and of the reheating temperature governing the iDM production.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.34230",
  "author_total": 2,
  "authors": [
    {
      "name": "Krzysztof Jodłowski"
    },
    {
      "name": "Chih-Ting Lu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0m7e8qw02jsq8.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.34230",
  "fulltext_url": null,
  "id": "0m7e8qw02jsq8",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.34230",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.CO"
    ],
    [
      "arxiv",
      "hep-ph"
    ],
    [
      "openalex",
      "3106|Dark Matter and Cosmic Phenomena"
    ]
  ],
  "openalex": "W7214701020",
  "pdf_url": "https://arxiv.org/pdf/2609.34230",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/0m7e8qw02jsq8.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2609.34230",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.34230"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Freeze-in of anapole and charge-radius inelastic dark matter: X-ray probes of a decoupled vector portal",
  "title_text": "Freeze-in of anapole and charge-radius inelastic dark matter: X-ray probes of a decoupled vector portal",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/0m7e8qw02jsq8",
  "venue": "arXiv",
  "versions": []
}