{
  "abstract": "A light neutrinophilic scalar $ϕ$, which couples predominantly to neutrinos, can be probed through leptonic meson decays for scalar masses $10~\\mathrm{MeV}\\lesssim m_ϕ\\lesssim\\mathcal{O}(100)~\\mathrm{MeV}$. We study neutrinophilic-scalar emission in $D$-meson decays at BESIII and the future Super Tau-Charm Facility (STCF), focusing on $D_{(s)}^+\\to e^+\\barν_αϕ$. Accounting for the $m_ϕ$-dependent missing-mass squared ($M_{\\rm miss}^2$) distribution within the experimentally selected region, we find the resulting $D^+$ constraint to be substantially weaker than previous estimates based on the integrated three-body decay rate. Extending the $M_{\\rm miss}^2$ coverage provides sensitivity to heavier scalars. With the full kinematic range of $M_{\\rm miss}^2$ and an integrated luminosity of $1~\\mathrm{ab}^{-1}$, the projected STCF sensitivities surpass the existing kaon bound for $m_ϕ\\gtrsim 380~\\mathrm{MeV}$ in the $D^+$ decay and $m_ϕ\\gtrsim 310~\\mathrm{MeV}$ in the $D_s^+$ decay. We further discuss direct searches for $D_{(s)}^+\\toμ^+\\barν_αϕ$ and their potential for probing the neutrinophilic scalar. A complete analytic expression for the three-body decay width is also derived with full dependence on the scalar and charged-lepton masses, including its behavior in the $m_ϕ\\to 0$ and $m_\\ell\\to 0$ limits.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.08606",
  "author_total": 2,
  "authors": [
    {
      "name": "Jin-Man Cai"
    },
    {
      "name": "Gang Li"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/frw1xmas1yymx.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.08606",
  "fulltext_url": null,
  "id": "frw1xmas1yymx",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.08606",
  "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|Particle physics theoretical and experimental studies"
    ]
  ],
  "openalex": "W7221019153",
  "pdf_url": "https://arxiv.org/pdf/2610.08606",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/frw1xmas1yymx.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:22Z",
      "native_id": "2610.08606",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.08606"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Missing Mass Matters: Neutrinophilic Scalar in $D$-Meson Decays",
  "title_text": "Missing Mass Matters: Neutrinophilic Scalar in D-Meson Decays",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:22Z",
  "url": "https://research.draconitic.com/paper/frw1xmas1yymx",
  "venue": "arXiv",
  "versions": []
}