{
  "abstract": "Femtoscopic measurements of two-pion Bose--Einstein correlations have established that particle-emitting sources in heavy-ion collisions are well described by Lévy $α$-stable distributions, motivating systematic studies across a wide range of collision energies. In this work, we present a three-dimensional femtoscopic analysis of pion pairs in Au+Au collisions simulated with the UrQMD model for collision energies $\\sqrt{s_{NN}}=3$--$27\\,\\mathrm{GeV}$, taking the RHIC BES-II range of collider and fixed target experiment energies for reference. Using Lévy-type source parameterisations, we extract the Lévy index $α$, the three-dimensional radii $R_\\mathrm{out}$, $R_\\mathrm{side}$, $R_\\mathrm{long}$, and the pair multiplicity parameter $λ^{*}$ (related to the correlation strength $λ$). We investigate their dependence on the transverse mass ($m_T$) and collision energy, along with derived quantities such as the radius difference $R_{\\mathrm{diff}}^2=R_{\\mathrm{out}}^2-R_\\mathrm{side}^2$ and the ratio $R_\\mathrm{out}/R_\\mathrm{side}$. We find that $R_\\mathrm{out,side,long}$ all decrease with increasing $m_T$ and increase with collision energy, consistent with collective expansion, $R_\\mathrm{long}$ showing the strongest and $R_\\mathrm{side}$ the weakest energy dependence. The Lévy index $α$ decreases with collision energy, with a larger $m_T$-dependence towards higher energies. The $λ^{*}$ parameter is consistent with a constant close to unity in the absence of pions from long-lived resonances. These results provide a baseline for future comparisons with experimental measurements from the STAR Collaboration, contributing to constraints on the QCD phase diagram.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Eur. Phys. J. A 62, 208 (2026)",
  "arxiv": "2605.15717",
  "author_total": 4,
  "authors": [
    {
      "name": "Matyas Molnar"
    },
    {
      "name": "Daniel Kincses"
    },
    {
      "name": "Yan Huang"
    },
    {
      "name": "Mate Csanad"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5y8x3854t1ct1.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2605.15717",
  "fulltext_url": null,
  "id": "5y8x3854t1ct1",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2605.15717",
  "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-ex"
    ],
    [
      "arxiv",
      "nucl-th"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2605.15717",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5y8x3854t1ct1.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:31Z",
      "native_id": "2605.15717",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2605.15717"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    },
    {
      "field": "physics",
      "origin": "arxiv:nucl-ex",
      "subfield": "nuclear"
    }
  ],
  "title": "Pion emission source shape in UrQMD Au + Au collisions at STAR energies",
  "title_text": "Pion emission source shape in UrQMD Au + Au collisions at STAR energies",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:31Z",
  "url": "https://research.draconitic.com/paper/5y8x3854t1ct1",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1140/epja/s10050-026-01970-w",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}