{
  "abstract": "The COMET Phase-$α$ experiment, the initial beam-operation stage of the COMET muon-to-electron conversion programme at J-PARC, took place in 2023 and marked the first beam operation at the COMET facility. It served to commission the delivery of a bunched, slow-extracted 8 GeV proton beam and the muon beamline. Its objective was to demonstrate experimentally that low-momentum negative muons could be transported to the experimental area through the Transport Solenoid (TS). We report a measurement of the transported muon beam using the Range Counter, a dedicated detector that identifies stopped negative muons by detecting delayed electrons emitted after the muons stop in a copper absorber. From the measured decay-time spectra, we reconstruct the number of stopped muons, the corresponding momentum spectrum, and the transverse beam profile. The observation of the stopped-muon component demonstrates that slow negative muons were transported through the TS to the experimental area. The reconstructed momentum spectrum indicates that the transported beam is concentrated in the low-momentum region. The non-uniform transverse profile is qualitatively consistent with charge drift in the curved solenoidal magnetic field. A Geant4-based simulation reproduces the overall dependence on degrader thickness and detector position; the measured yields are systematically higher by roughly 30%. These results provide the first experimental benchmark of low-momentum negative-muon transport in COMET and establish the basis for future beam characterisation and production studies.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.02855",
  "author_total": 185,
  "authors": [
    {
      "name": "K Oishi"
    },
    {
      "name": "R Abramishvili"
    },
    {
      "name": "G Adamov"
    },
    {
      "name": "J.C Angelique"
    },
    {
      "name": "K Aoki"
    },
    {
      "name": "M Aoki"
    },
    {
      "name": "Y Arimoto"
    },
    {
      "name": "A.N.B Az"
    },
    {
      "name": "I Bagaturia"
    },
    {
      "name": "D Bauer"
    },
    {
      "name": "T Bouillaud"
    },
    {
      "name": "L del Buono"
    },
    {
      "name": "C Carloganu"
    },
    {
      "name": "N Chadeau"
    },
    {
      "name": "Y Chen"
    },
    {
      "name": "P Chetry"
    },
    {
      "name": "D Chokheli"
    },
    {
      "name": "T Clouvel"
    },
    {
      "name": "P.D Dauncey"
    },
    {
      "name": "S Dekkers"
    },
    {
      "name": "R Derveni"
    },
    {
      "name": "G Devidze"
    },
    {
      "name": "P.J Dornan"
    },
    {
      "name": "M.T Dubouchet"
    },
    {
      "name": "L.B Epshteyn"
    },
    {
      "name": "I Evtoukhovitch"
    },
    {
      "name": "P Evtoukhovitch"
    },
    {
      "name": "G Faure"
    },
    {
      "name": "S Fayer"
    },
    {
      "name": "G.V Fedotovich"
    },
    {
      "name": "Y Fujii"
    },
    {
      "name": "Y Fukao"
    },
    {
      "name": "E George"
    },
    {
      "name": "E.L Gillies"
    },
    {
      "name": "M Gouzevitch"
    },
    {
      "name": "D.N Grigoriev"
    },
    {
      "name": "E Hamada"
    },
    {
      "name": "I.H Hashim"
    },
    {
      "name": "S Hashimoto"
    },
    {
      "name": "M Higashide"
    },
    {
      "name": "Y Higuchi"
    },
    {
      "name": "N Hiroshima"
    },
    {
      "name": "Y Igarashi"
    },
    {
      "name": "F.V Ignatov"
    },
    {
      "name": "M Iio"
    },
    {
      "name": "M Ikeno"
    },
    {
      "name": "K Ishibashi"
    },
    {
      "name": "T Itahashi"
    },
    {
      "name": "A Jansen"
    },
    {
      "name": "R Jeena"
    },
    {
      "name": "O Jeremy"
    },
    {
      "name": "X Jiang"
    },
    {
      "name": "P.M Jonsson"
    },
    {
      "name": "Y Kageyama"
    },
    {
      "name": "V Kalinnikov"
    },
    {
      "name": "E Kaneva"
    },
    {
      "name": "F Kapusta"
    },
    {
      "name": "K Kawagoe"
    },
    {
      "name": "R Kawashima"
    },
    {
      "name": "N Kazak"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/42frpaf5tv7t2.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.02855",
  "fulltext_url": null,
  "id": "42frpaf5tv7t2",
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  "landing_url": "https://hal.science/hal-05829677v1",
  "language": "en",
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  "licence_label": "CC BY 4.0",
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  "pdf_url": "https://arxiv.org/pdf/2610.02855",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/42frpaf5tv7t2.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "hal-05829677",
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      "url": "https://hal.science/hal-05829677v1"
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      "native_id": "2610.02855",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.02855"
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  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.ins-det",
      "subfield": "applied-instrumentation"
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    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "First measurement of the low-momentum negative-muon beam for the muon-to-electron conversion experiment at J-PARC",
  "title_text": "First measurement of the low-momentum negative-muon beam for the muon-to-electron conversion experiment at J-PARC",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:45Z",
  "url": "https://research.draconitic.com/paper/42frpaf5tv7t2",
  "venue": "HAL",
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}