{
  "abstract": "We investigate thermal leptogenesis in an extension of the Type-I seesaw in which a real singlet scalar couples non-diagonally to the right-handed neutrinos. The interactions $-y_{ij}ϕN_iN_j$, with $i\\neq j$, introduce new sources of CP violation in heavy-neutrino decays with a negligible enhancement of the standard leptonic washout. We derive an analytic upper bound on the scalar-induced CP asymmetry and present numerical results using fully flavoured Boltzmann equations and the density-matrix formalism. We show that the observed baryon asymmetry can be generated with a hierarchical right-handed-neutrino spectrum at the electroweak scale. In the minimal Type-I seesaw, lowering the scale of decay leptogenesis typically requires either a tuned quasi-degeneracy of the right-handed-neutrino masses or cancellations between the tree-level and one-loop contributions to the light-neutrino masses, while hierarchical leptogenesis instead requires a high scale that aggravates the Higgs hierarchy problem. This singlet-scalar extension appears to avoid these tensions, allowing successful leptogenesis with a hierarchical right-handed-neutrino spectrum down to the electroweak scale.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.24990",
  "author_total": 1,
  "authors": [
    {
      "name": "Angus Spalding"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5w94ydqds36c9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.24990",
  "fulltext_url": null,
  "id": "5w94ydqds36c9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.24990",
  "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|Particle physics theoretical and experimental studies"
    ]
  ],
  "openalex": "W7214036587",
  "pdf_url": "https://arxiv.org/pdf/2609.24990",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-21",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5w94ydqds36c9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:20Z",
      "native_id": "2609.24990",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.24990"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Three-Flavoured Thermal Leptogenesis Without Tuning",
  "title_text": "Three-Flavoured Thermal Leptogenesis Without Tuning",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:20Z",
  "url": "https://research.draconitic.com/paper/5w94ydqds36c9",
  "venue": "arXiv",
  "versions": []
}