{
  "abstract": "The ATOMKI anomalies motivate the possibility of a new particle, the X17, with a mass of 17 MeV and weak couplings to nuclei and electrons. Such a particle may be produced at the LHC, travel 480 m in the far-forward direction, and decay to $e^+e^-$ in FASER. In this paper, previous FASER searches for dark photons and axion-like particles (ALPs) are combined and interpreted as searches for a candidate X17 particle, the protophobic vector boson. The searches use data collected from $pp$ collisions at $\\sqrt{s} = 13.6$ TeV in LHC Run 3 from 2022 for the dark photon search and from 2022-2023 for the ALP search. No excess events are found above the expected background, and the combined null results exclude a previously-unconstrained \"low-coupling window\" with electron coupling $6 \\times 10^{-5} < ε_e < 1.2 \\times 10^{-4}$. A \"high-coupling window\" remains.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.03904",
  "author_total": 136,
  "authors": [
    {
      "name": "FASER Collaboration"
    },
    {
      "name": "Roshan Mammen Abraham"
    },
    {
      "name": "Xiaocong Ai"
    },
    {
      "name": "Saul Alonso Monsalve"
    },
    {
      "name": "John Anders"
    },
    {
      "name": "Emma Kate Anderson"
    },
    {
      "name": "Akitaka Ariga"
    },
    {
      "name": "Tomoko Ariga"
    },
    {
      "name": "Jeremy Atkinson"
    },
    {
      "name": "Florian U. Bernlochner"
    },
    {
      "name": "Jianming Bian"
    },
    {
      "name": "Tobias Boeckh"
    },
    {
      "name": "Eliot Bornand"
    },
    {
      "name": "Jamie Boyd"
    },
    {
      "name": "Lydia Brenner"
    },
    {
      "name": "Angela Burger"
    },
    {
      "name": "Franck Cadoux"
    },
    {
      "name": "Haichuan Cao"
    },
    {
      "name": "Roberto Cardella"
    },
    {
      "name": "David W. Casper"
    },
    {
      "name": "Charlotte Cavanagh"
    },
    {
      "name": "Shiyang Chen"
    },
    {
      "name": "Xin Chen"
    },
    {
      "name": "Xing Cheng"
    },
    {
      "name": "Dhruv Chouhan"
    },
    {
      "name": "Emily Chown"
    },
    {
      "name": "Andrea Coccaro"
    },
    {
      "name": "Fabio Cufino"
    },
    {
      "name": "Stephane Débieux"
    },
    {
      "name": "Ansh Desai"
    },
    {
      "name": "Sergey Dmitrievsky"
    },
    {
      "name": "Radu Dobre"
    },
    {
      "name": "Monica D'Onofrio"
    },
    {
      "name": "Sinead Eley"
    },
    {
      "name": "Yannick Favre"
    },
    {
      "name": "Jonathan L. Feng"
    },
    {
      "name": "Carlo Alberto Fenoglio"
    },
    {
      "name": "Didier Ferrere"
    },
    {
      "name": "Max Fieg"
    },
    {
      "name": "Wissal Filali"
    },
    {
      "name": "Elena Firu"
    },
    {
      "name": "Haruhi Fujimori"
    },
    {
      "name": "Edward Galantay"
    },
    {
      "name": "Ali Garabaglu"
    },
    {
      "name": "Stephen Gibson"
    },
    {
      "name": "Sergio Gonzalez-Sevilla"
    },
    {
      "name": "Yuri Gornushkin"
    },
    {
      "name": "Yotam Granov"
    },
    {
      "name": "Jinjing Gu"
    },
    {
      "name": "Carl Gwilliam"
    },
    {
      "name": "Elie Hammou"
    },
    {
      "name": "Daiki Hayakawa"
    },
    {
      "name": "Michael Holzbock"
    },
    {
      "name": "Shih-Chieh Hsu"
    },
    {
      "name": "Zhen Hu"
    },
    {
      "name": "Giuseppe Iacobucci"
    },
    {
      "name": "Tomohiro Inada"
    },
    {
      "name": "Luca Iodice"
    },
    {
      "name": "Sune Jakobsen"
    },
    {
      "name": "Cesar Jesus-Valls"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cg9eeejg78246.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.03904",
  "fulltext_url": null,
  "id": "cg9eeejg78246",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.03904",
  "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"
    ],
    [
      "arxiv",
      "hep-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.03904",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/cg9eeejg78246.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T15:21:25Z",
      "native_id": "2611.03904",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.03904"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Constraints on a Long-Lived X17 Vector Boson with FASER",
  "title_text": "Constraints on a Long-Lived X17 Vector Boson with FASER",
  "type": "preprint",
  "updated_at": "2026-11-06T18:21:01Z",
  "url": "https://research.draconitic.com/paper/cg9eeejg78246",
  "venue": "arXiv",
  "versions": []
}