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    "title": "Pulsed-beam muonium hyperfine spectroscopy and time-domain Rabi analysis",
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    "area": "Atomic and fundamental physics / unstable-atom microwave spectroscopy",
    "topic": "Physics",
    "year": 2020,
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      "N. Kawamura",
      "N. Kurosawa",
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      "N. Saito",
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      "statement": "# Pulsed-beam muonium hyperfine spectroscopy and time-domain Rabi analysis\n\nThe MuSEUM collaboration demonstrated near-zero-field muonium ground-state hyperfine spectroscopy at J-PARC using a pulsed muon beam and detectors designed for high event rates. Kanda and colleagues reported a frequency-scan result of 4463.302±0.004 MHz. Nishimura and colleagues developed an analysis of the time-dependent Rabi signal that jointly fits frequency detuning and microwave-field strength, and applied it to later data to obtain a zero-density hyperfine interval of 4,463,301.61±0.71 kHz, with the quoted uncertainty statistical. Their simulations identified conditions in which concentrating measurements at a suitable detuning could improve statistical precision.\n\n## Scientific scope\n\nThe time-domain analysis uses a model of the microwave-field distribution and muon stopping positions, and determines the magnitude of detuning without its sign. The experimental demonstration combined measurements at multiple frequencies and powers. Its precision gain depends on the simulated conditions; it is not a universal factor-of-two guarantee or a replacement for the more precise historical high-field measurement. Gas-density corrections, frequency references, detector response and residual microwave drift remain relevant. Future beam upgrades and hertz-level goals were proposed rather than demonstrated.\n\n## Reading status\n\nThis is a source-linked WRS catalogue note. A full explanatory guide and independent scientific reconstruction have not been completed for this entry. Read the identified original work for its complete narrative and arguments.\n\n## People and systems\n\nS. Nishimura; H. A. Torii; Y. Fukao; T. U. Ito; M. Iwasaki; S. Kanda; K. Kawagoe; D. Kawall; N. Kawamura; N. Kurosawa; Y. Matsuda; T. Mibe; Y. Miyake; N. Saito; K. Sasaki; Y. Sato; S. Seo; P. Strasser; T. Suehara; K. S. Tanaka; T. Tanaka; J. Tojo; A. Toyoda; Y. Ueno; T. Yamanaka; T. Yamazaki; H. Yasuda; T. Yoshioka; K. Shimomura; Y. Ikedo; K. Ishida; K. M. Kojima\n\nThese are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.\n\n\n\n## Original sources\n\n- [Rabi-Oscillation Spectroscopy of the Hyperfine Structure of Muonium Atoms (arXiv2007.12386v2)](https://arxiv.org/pdf/2007.12386v2)\n- [New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam (arXiv2004.05862v2)](https://arxiv.org/pdf/2004.05862v2)\n",
      "summary": "The MuSEUM collaboration demonstrated near-zero-field muonium ground-state hyperfine spectroscopy at J-PARC using a pulsed muon beam and detectors designed for high event rates. Kanda and colleagues reported a frequency-scan result of 4463.302±0.004 MHz. Nishimura and colleagues developed an analysis of the time-dependent Rabi signal that jointly fits frequency detuning and microwave-field strength, and applied it to later data to obtain a zero-density hyperfine interval of 4,463,301.61±0.71 kHz, with the quoted uncertainty statistical. Their simulations identified conditions in which concentrating measurements at a suitable detuning could improve statistical precision.",
      "title": "Pulsed-beam muonium hyperfine spectroscopy and time-domain Rabi analysis"
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    "edition": "2026-10-28.1",
    "id": "museum-pulsed-beam-muonium-hyperfine-rabi-spectroscopy-2020",
    "entry_id": "museum-pulsed-beam-muonium-hyperfine-rabi-spectroscopy-2020",
    "revision": 1,
    "title": "Pulsed-beam muonium hyperfine spectroscopy and time-domain Rabi analysis",
    "context": "Atomic and fundamental physics / unstable-atom microwave spectroscopy",
    "track": "Source-reported experimental result or reusable measurement method",
    "band": "B",
    "modifier": "+",
    "status": "PROVISIONAL_EDITORIAL",
    "assessed_on": "2026-10-28",
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    "what_changed": "The MuSEUM collaboration demonstrated near-zero-field muonium ground-state hyperfine spectroscopy at J-PARC using a pulsed muon beam and detectors designed for high event rates. Kanda and colleagues reported a frequency-scan result of 4463.302±0.004 MHz. Nishimura and colleagues developed an analysis of the time-dependent Rabi signal that jointly fits frequency detuning and microwave-field strength, and applied it to later data to obtain a zero-density hyperfine interval of 4,463,301.61±0.71 kHz, with the quoted uncertainty statistical. Their simulations identified conditions in which concentrating measurements at a suitable detuning could improve statistical precision.",
    "scope": "The MuSEUM collaboration demonstrated near-zero-field muonium ground-state hyperfine spectroscopy at J-PARC using a pulsed muon beam and detectors designed for high event rates. Kanda and colleagues reported a frequency-scan result of 4463.302±0.004 MHz. Nishimura and colleagues developed an analysis of the time-dependent Rabi signal that jointly fits frequency detuning and microwave-field strength, and applied it to later data to obtain a zero-density hyperfine interval of 4,463,301.61±0.71 kHz, with the quoted uncertainty statistical. Their simulations identified conditions in which concentrating measurements at a suitable detuning could improve statistical precision. The time-domain analysis uses a model of the microwave-field distribution and muon stopping positions, and determines the magnitude of detuning without its sign. The experimental demonstration combined measurements at multiple frequencies and powers. Its precision gain depends on the simulated conditions; it is not a universal factor-of-two guarantee or a replacement for the more precise historical high-field measurement. Gas-density corrections, frequency references, detector response and residual microwave drift remain relevant. Future beam upgrades and hertz-level goals were proposed rather than demonstrated.",
    "evidence_summary": "The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The time-domain analysis uses a model of the microwave-field distribution and muon stopping positions, and determines the magnitude of detuning without its sign. The experimental demonstration combined measurements at multiple frequencies and powers. Its precision gain depends on the simulated conditions; it is not a universal factor-of-two guarantee or a replacement for the more precise historical high-field measurement. Gas-density corrections, frequency references, detector response and residual microwave drift remain relevant. Future beam upgrades and hertz-level goals were proposed rather than demonstrated.",
    "references": [
      {
        "title": "Rabi-Oscillation Spectroscopy of the Hyperfine Structure of Muonium Atoms (arXiv2007.12386v2)",
        "url": "https://arxiv.org/pdf/2007.12386v2",
        "locator": "Original scoped contribution, statement/method and evidence limits; source-specific attribution retained."
      },
      {
        "title": "New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam (arXiv2004.05862v2)",
        "url": "https://arxiv.org/pdf/2004.05862v2",
        "locator": "Original scoped contribution, statement/method and evidence limits; source-specific attribution retained."
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