{
  "abstract": "Radiative $V\\to Pγ$ and $P\\to Vγ$ decays are conventionally described using constituent-quark mass differences and phenomenological wavefunction-overlap factors as sources of flavour-symmetry breaking. We investigate whether the overlap factors can instead be understood as the effect of mixing of the $η$ and $η^\\prime$ with an additional pseudoscalar state, described by an $SO(4)$ rotation among four basis states. A global fit to current data yields a significantly better description than the corresponding three-state limit without overlap factors, while preserving the established $η$-$η^\\prime$ and vector-meson mixing angles, and shows that the additional state mixes predominantly with the non-strange component. The conventional overlap-factor description is recovered exactly as the special case in which this mixing is purely non-strange. The non-strange pattern disfavours both a flavour-singlet admixture, as expected from mixing with a pseudoscalar glueball, and the gluonium scenario considered in previous analyses. Radiative decays therefore provide no compelling evidence for gluonium in the $η^\\prime$, and the overlap factors are better interpreted in terms of a radially excited non-strange state.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.25216",
  "author_total": 2,
  "authors": [
    {
      "name": "Rafel Escribano"
    },
    {
      "name": "Emilio Royo"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ejq3h6zkys3xm.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.25216",
  "fulltext_url": null,
  "id": "ejq3h6zkys3xm",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.25216",
  "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",
      "hep-ex"
    ],
    [
      "arxiv",
      "hep-ph"
    ],
    [
      "openalex",
      "3106|Quantum Chromodynamics and Particle Interactions"
    ]
  ],
  "openalex": "W7223021257",
  "pdf_url": "https://arxiv.org/pdf/2610.25216",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ejq3h6zkys3xm.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:52Z",
      "native_id": "2610.25216",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.25216"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Is there gluonium in the $η^\\prime$? The flavour structure of $η$ and $η^\\prime$ mixing in radiative $V\\to Pγ$ and $P\\to Vγ$ decays",
  "title_text": "Is there gluonium in the η^′? The flavour structure of η and η^′ mixing in radiative V→ Pγ and P→ Vγ decays",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:41Z",
  "url": "https://research.draconitic.com/paper/ejq3h6zkys3xm",
  "venue": "arXiv",
  "versions": []
}