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    "title": "Positronium fine-structure spectroscopy and diagnosis of asymmetric resonance lines",
    "summary": "Gurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget.",
    "boundary": "The reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.",
    "area": "Atomic and fundamental physics / positronium microwave spectroscopy",
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        "description": "The reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.",
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      "statement": "# Positronium fine-structure spectroscopy and diagnosis of asymmetric resonance lines\n\nGurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget.\n\n## Scientific scope\n\nThe reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.\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\nL. Gurung; T. J. Babij; S. D. Hogan; D. B. Cassidy; J. Pérez-Ríos\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- [Precision Microwave Spectroscopy of the Positronium n=2 Fine Structure (PRL125073002)](https://discovery.ucl.ac.uk/10107934/1/PhysRevLett.125.073002.pdf)\n- [Observation of asymmetric line shapes in precision microwave spectroscopy of the positronium 2tripletS1 to2tripletPJ(J=1,2) fine-structure intervals (PRA103042805)](https://discovery.ucl.ac.uk/10126237/1/PhysRevA.103.042805.pdf)\n- [Line-shape modeling in microwave spectroscopy of the positronium n=2 fine-structure intervals (PRA104062810)](https://discovery.ucl.ac.uk/id/eprint/10140797/1/PhysRevA.104.062810.pdf)\n",
      "summary": "Gurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget.",
      "title": "Positronium fine-structure spectroscopy and diagnosis of asymmetric resonance lines"
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    "scope": "Gurung and colleagues used laser-prepared metastable positronium, microwave transitions and annihilation-time detection to study the n=2 fine structure. Their 2021 analysis reported 18,501.02±0.57(stat)±0.323(syst) MHz for the 2³S₁ → 2³P₀ interval, approximately 4.2 standard deviations above its cited QED prediction under that error budget. The J=1 and J=2 spectra revealed asymmetric lines. A subsequent model by Akopyan and colleagues showed that frequency-dependent microwave reflections could produce shifts of several MHz, including shifts of apparently symmetric lines, exposing a systematic uncertainty beyond the earlier budget. The reported frequencies depend on line-shape assumptions, magnetic-field extrapolation, laser alignment and electric-field and Doppler estimates. The detailed experiment added recoil Doppler uncertainty omitted in 2020 without changing its central value. Subsequent numerical modeling suggested a conservative reflection-related uncertainty of about 4 MHz; this is a model estimate, not a measured correction or a verified probability distribution. Unmodeled chamber elements prevent direct correction of the original data. The earlier 4.2-standard-deviation comparison therefore does not establish a surviving anomaly, new force or failure of QED. Asymmetric J=1 and J=2 fit centres are diagnostics, not reliable precise intervals. The modeled quantum-interference channels were too small to explain the MHz effects; other unmodeled mechanisms and later experimental comparisons remain open.",
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