{
  "abstract": "We formulate, within a fixed FSI-improved amplitude convention, a zero-locus diagnostic for the direct contact term in $ϕ\\toπ^+π^-π^0$. The resonant $ρπ$ contribution is dressed channel by channel with the complex Omnès function, the direct term is multiplied by the averaged Omnès factor, and a real constant background is retained as a smooth residual amplitude. In this convention, $F^{\\rm FSI}=R+c e^{iδ_{\\rm dir}}D$ with $c=g_{\\phi3π}^{\\rm eff}$, and the difference of two constrained invariant-mass gradients of the reduced Dalitz density gives a local quadratic identity for $c$ on the zero-contour. The construction provides a closure and stability diagnostic complementary to a global Dalitz-plot fit. For the benchmark input $g_{\\phi3π}^{\\rm eff}=-24.0~{\\rm GeV}^{-3}$, we identify a numerically stable zero-contour branch around $M_{+0}=0.460\\pm0.025~{\\rm GeV}$ and $M_{+-}\\le0.560~{\\rm GeV}$, where the tight-contour median estimator reproduces $g_{\\phi3π}^{\\rm est}\\simeq -24.0~{\\rm GeV}^{-3}$, a closure recovery of the injected coupling within the chosen FSI-improved convention rather than an independent extraction. We further vary the mass-window selection of the branch. The median remains close to the injected value under shifts of the $M_{+0}$ window and moderate changes of its width, while the mean and standard deviation are more sensitive to outlier points near unstable quadratic branches. The method therefore identifies Dalitz-plane regions where the direct-term interference is locally well-conditioned and provides useful guidance for control-region choices and systematic variations in future global fits.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.10094",
  "author_total": 2,
  "authors": [
    {
      "name": "Seung-il Nam"
    },
    {
      "name": "Jung Keun Ahn"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ebf1w8bhynbf3.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.10094",
  "fulltext_url": null,
  "id": "ebf1w8bhynbf3",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.10094",
  "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"
    ],
    [
      "arxiv",
      "nucl-th"
    ],
    [
      "openalex",
      "3106|Quantum Chromodynamics and Particle Interactions"
    ]
  ],
  "openalex": "W7212129492",
  "pdf_url": "https://arxiv.org/pdf/2609.10094",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-09",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ebf1w8bhynbf3.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:12Z",
      "native_id": "2609.10094",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.10094"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    },
    {
      "field": "physics",
      "origin": "arxiv:nucl-th",
      "subfield": "nuclear"
    }
  ],
  "title": "Zero-locus diagnostic of the direct contact term in $ϕ\\toπ^+π^-π^0$",
  "title_text": "Zero-locus diagnostic of the direct contact term in ϕ→π^+π^-π^0",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:12Z",
  "url": "https://research.draconitic.com/paper/ebf1w8bhynbf3",
  "venue": "arXiv",
  "versions": []
}