{
  "abstract": "Using $20.3~{\\rm fb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at $\\sqrt{s}=3.773~{\\rm GeV}$, we perform the first amplitude analysis of the decay $D^+\\toπ^+ηη$. The intermediate process $D^+\\to a_0(980)^+η$, $a_0(980)^+\\toπ^+η$, is observed as the only significant component in the amplitude analysis, and its branching fraction is measured to be $(3.67\\pm0.12_{\\rm stat}\\pm0.06_{\\rm syst})\\times10^{-3}$. The $π^+η$ mass spectrum associated with $a_0(980)^+η$ production exhibits a line shape that differs substantially from those observed in $D_{(s)}\\to a_0(980)π$ and $D^0\\to a_0(980)^-e^+ν_e$ decays. We examine several conventional descriptions of the $a_0(980)$ amplitude, including Flatté, dispersively modified Flatté, $T$-matrix, and $K$-matrix parameterizations. With reference $a_0(980)$ parameters, neither these models nor their extensions including additional small resonant or non-resonant amplitudes reproduce the observed line shape satisfactorily. When the $a_0(980)$ parameters are allowed to float, satisfactory fits can be obtained, but the pole mass is driven well above the $K\\bar K$ threshold, inconsistent with the near-threshold character of the $a_0(980)$. The results reveal a tension between fit quality and the physical pole position in conventional direct-production amplitude models.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2606.17724",
  "author_total": 722,
  "authors": [
    {
      "name": "BESIII Collaboration"
    },
    {
      "name": "M. Ablikim"
    },
    {
      "name": "M. N. Achasov"
    },
    {
      "name": "P. Adlarson"
    },
    {
      "name": "X. C. Ai"
    },
    {
      "name": "R. Aliberti"
    },
    {
      "name": "A. Amoroso"
    },
    {
      "name": "Q. An"
    },
    {
      "name": "Y. Bai"
    },
    {
      "name": "O. Bakina"
    },
    {
      "name": "Y. Ban"
    },
    {
      "name": "H. -R. Bao"
    },
    {
      "name": "V. Batozskaya"
    },
    {
      "name": "K. Begzsuren"
    },
    {
      "name": "N. Berger"
    },
    {
      "name": "M. Berlowski"
    },
    {
      "name": "M. Bertani"
    },
    {
      "name": "D. Bettoni"
    },
    {
      "name": "F. Bianchi"
    },
    {
      "name": "E. Bianco"
    },
    {
      "name": "A. Bortone"
    },
    {
      "name": "I. Boyko"
    },
    {
      "name": "R. A. Briere"
    },
    {
      "name": "A. Brueggemann"
    },
    {
      "name": "H. Cai"
    },
    {
      "name": "M. H. Cai"
    },
    {
      "name": "X. Cai"
    },
    {
      "name": "A. Calcaterra"
    },
    {
      "name": "G. F. Cao"
    },
    {
      "name": "N. Cao"
    },
    {
      "name": "S. A. Cetin"
    },
    {
      "name": "X. Y. Chai"
    },
    {
      "name": "J. F. Chang"
    },
    {
      "name": "G. R. Che"
    },
    {
      "name": "Y. Z. Che"
    },
    {
      "name": "C. H. Chen"
    },
    {
      "name": "Chao Chen"
    },
    {
      "name": "G. Chen"
    },
    {
      "name": "H. S. Chen"
    },
    {
      "name": "H. Y. Chen"
    },
    {
      "name": "M. L. Chen"
    },
    {
      "name": "S. J. Chen"
    },
    {
      "name": "S. L. Chen"
    },
    {
      "name": "S. M. Chen"
    },
    {
      "name": "T. Chen"
    },
    {
      "name": "X. R. Chen"
    },
    {
      "name": "X. T. Chen"
    },
    {
      "name": "X. Y. Chen"
    },
    {
      "name": "Y. B. Chen"
    },
    {
      "name": "Y. Q. Chen"
    },
    {
      "name": "Y. Q. Chen"
    },
    {
      "name": "Z. J. Chen"
    },
    {
      "name": "Z. K. Chen"
    },
    {
      "name": "S. K. Choi"
    },
    {
      "name": "X. Chu"
    },
    {
      "name": "G. Cibinetto"
    },
    {
      "name": "F. Cossio"
    },
    {
      "name": "J. Cottee-Meldrum"
    },
    {
      "name": "J. J. Cui"
    },
    {
      "name": "H. L. Dai"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aj416kg7bjry6.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.17724",
  "fulltext_url": null,
  "id": "aj416kg7bjry6",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.17724",
  "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-ex"
    ],
    [
      "openalex",
      "3106|Quantum Chromodynamics and Particle Interactions"
    ]
  ],
  "openalex": "W7164997633",
  "pdf_url": "https://arxiv.org/pdf/2606.17724",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/aj416kg7bjry6.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:32Z",
      "native_id": "2606.17724",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.17724"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Observation of an Altered $a_{0}(980)$ Line shape in $D^{+} \\rightarrow π^{+}ηη$",
  "title_text": "Observation of an Altered a_0(980) Line shape in D^+ → π^+ηη",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:28Z",
  "url": "https://research.draconitic.com/paper/aj416kg7bjry6",
  "venue": "arXiv",
  "versions": []
}