{
  "abstract": "We present the first calculation of the radiative decays $J/ψ,ψ(2S)\\rightarrowγη^{(\\prime)}$ in perturbative QCD that includes the order-$q^{2}$ relativistic corrections in all three short-distance contributions, namely the quark-antiquark, two-gluon, and QED contributions. The amplitudes are found to be remarkably insensitive to the light-cone distribution amplitude and to the light-quark mass, a robustness that persists through order $q^{2}$ and makes the predictions correspondingly reliable. The relativistic correction enhances the $J/ψ$ branching ratios by roughly a factor of 2, narrowing their shortfall from experiment, whereas for the $ψ(2S)$ it is about twice as large as for the $J/ψ$ and the low-order expansion converges poorly. In two representative $η$--$η^{\\prime}$ mixing schemes, the ratio $\\mathcal{R}_{1S}=\\mathcal{B}(γη^{\\prime})/\\mathcal{B}(γη)$ proves sharply sensitive to the mixing angle and favors the smaller of the two. The predicted $ψ(2S)$ rates lie well above the data in both channels, already at leading order, and most severely for the anomalously small $γη$ channel. Such a discrepancy suggests that a mechanism beyond the hard perturbative process is at work. As a physically motivated attempt, we explore the $η_{c}$-mixing contribution, which adds coherently to the perturbative one and is comparable to it in the $γη$ channel, and find that the interference can bring the $ψ(2S)$ rates into agreement with the data, although its extraction is limited by a strong sensitivity to the mixing parameters.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Phys. Rev. D 114, 074003 (2026)",
  "arxiv": "2607.23737",
  "author_total": 3,
  "authors": [
    {
      "name": "Jun-Kang He"
    },
    {
      "name": "Chao-Jie Fan"
    },
    {
      "name": "Cong Wang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9r6jaegynyq75.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.23737",
  "fulltext_url": null,
  "id": "9r6jaegynyq75",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.23737",
  "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-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2607.23737",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9r6jaegynyq75.ris",
  "sources": [
    {
      "first_seen": "2026-11-02T12:21:15Z",
      "native_id": "2607.23737",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.23737"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Radiative decays of $J/ψ,\\,ψ(2S)\\rightarrowγη^{(\\prime)}$ in perturbative QCD with relativistic corrections",
  "title_text": "Radiative decays of J/ψ, ψ(2S)→γη^(′) in perturbative QCD with relativistic corrections",
  "type": "preprint",
  "updated_at": "2026-11-04T15:20:50Z",
  "url": "https://research.draconitic.com/paper/9r6jaegynyq75",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/jsxb-5335",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}