{
  "abstract": "The first observation of a new meson state decaying into $B_c^+$ and a photon is presented using a dataset of $pp$ collisions at a centre-of-mass energy $\\sqrt{s} = 13$\\,\\TeV collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 140\\,fb$^{-1}$. The $B_c^+$ mesons are reconstructed from a three-muon final state from $B_c^+\\to J/ψ(μ^+μ^-)μ^+ν_μX$ decays, along with photons reconstructed via conversions to electron-positron pairs in the detector material. The new state is observed with a significance that exceeds 8 standard deviations. The mass difference between the new meson state and the ground-state $B_c^+$ meson is measured to be $64.5 \\pm 1.4\\text{(stat.)}^{+1.0}_{-1.4}\\text{(syst.)}$ MeV. This corresponds to a mass for the observed state of $6339.0 \\pm 1.4\\text{(stat.)}^{+1.0}_{-1.4}\\text{(syst.)}\\pm 0.3\\,\\,(m_{B_c^+})$ MeV, where the last uncertainty is due to the precision of the best knowledge of the $B_c^+$ meson mass. The low mass difference value matches the theory expectations for the lowest vector state of the $\\bar{b}c$ system, the $B_c^{*+}$ meson.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Phys. Rev. Lett. 137 (2026) 141901",
  "arxiv": "2605.16228",
  "author_total": 1,
  "authors": [
    {
      "name": "ATLAS Collaboration"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/923tcxgdet8nw.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2605.16228",
  "fulltext_url": null,
  "id": "923tcxgdet8nw",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2605.16228",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2605.16228",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/923tcxgdet8nw.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:01Z",
      "native_id": "2605.16228",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2605.16228"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Observation of a $B_c^{*+}$ meson with the ATLAS detector",
  "title_text": "Observation of a B_c^*+ meson with the ATLAS detector",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:01Z",
  "url": "https://research.draconitic.com/paper/923tcxgdet8nw",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/vrxp-zkbs",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}