{
  "abstract": "The recent ATLAS observation of the $B_c^*(1S)$ meson fixes the ground-state hyperfine splitting and thereby determines the phase space for $B_c^*(1S)\\to B_c(1S)γ$. We study four $1S$ and $2S$ M1 radiative transitions using relativistic Salpeter wave functions calibrated to the measured ground-state masses, obtaining $Γ[B_c^*(1S)\\to B_c(1S)γ]=5.24\\times10^{-2}$~keV. The allowed transitions show no radial cancellation, whereas the hindered $2S\\to1S$ amplitudes are residuals of an approximately twenty-fold cancellation across the radial node. A quark-line-resolved analysis shows a strong asymmetry in the crossed hindered channel: the $b$-emission contribution undergoes an $\\mathcal O(10^2)$ internal cancellation while the $\\bar c$ contribution remains at $\\mathcal O(20)$. The corresponding unsigned line strengths show that the small $b$-current is generated by enhanced cancellation rather than by a smaller unsigned contribution. The unmeasured $B_c^*(2S)$ mass remains the main limitation on the $2S\\to2S$ radiative width.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.00138",
  "author_total": 1,
  "authors": [
    {
      "name": "Bing-Dong Wan"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/encetaw0tgh7z.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.00138",
  "fulltext_url": null,
  "id": "encetaw0tgh7z",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.00138",
  "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"
    ],
    [
      "openalex",
      "3106|Quantum Chromodynamics and Particle Interactions"
    ]
  ],
  "openalex": "W7216179493",
  "pdf_url": "https://arxiv.org/pdf/2610.00138",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/encetaw0tgh7z.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:03Z",
      "native_id": "2610.00138",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.00138"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "M1 Radiative Transitions in the $B_c$ System after the $B_c^\\ast(1S)$ Observation: Radial-Node Cancellation and Quark-Line Filtering",
  "title_text": "M1 Radiative Transitions in the B_c System after the B_c^∗(1S) Observation: Radial-Node Cancellation and Quark-Line Filtering",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:03Z",
  "url": "https://research.draconitic.com/paper/encetaw0tgh7z",
  "venue": "arXiv",
  "versions": []
}