BWhat changed
The Mu-MASS collaboration used a low-energy muon beam, carbon-foil muonium production and microwave-induced depletion of metastable atoms to measure the muonium n=2 Lamb shift. Ohayon and colleagues reported 1047.2±2.3(stat)±1.1(syst) MHz. Janka and colleagues then measured the isolated 2S1/2,F=0 to 2P1/2,F=1 transition at 580.6±6.8 MHz, deriving a Lamb shift of 1045.5±6.8 MHz and, together with the earlier transition measurement, a 2S hyperfine splitting of 559.6±7.2 MHz. The later line-shape analysis also identified a contribution from muonium in the n=3 excited state.
Scientific scope
The Mu-MASS collaboration used a low-energy muon beam, carbon-foil muonium production and microwave-induced depletion of metastable atoms to measure the muonium n=2 Lamb shift. Ohayon and colleagues reported 1047.2±2.3(stat)±1.1(syst) MHz. Janka and colleagues then measured the isolated 2S1/2,F=0 to 2P1/2,F=1 transition at 580.6±6.8 MHz, deriving a Lamb shift of 1045.5±6.8 MHz and, together with the earlier transition measurement, a 2S hyperfine splitting of 559.6±7.2 MHz. The later line-shape analysis also identified a contribution from muonium in the n=3 excited state. These are related measurements with simulated trajectory-dependent line shapes, microwave-power corrections and residual excited-state contamination. The isolated transition offers a route to lower systematic error, while its reported statistical uncertainty is larger than that of the earlier measurement. The excited-state population and combined hyperfine interval are inferred through the stated model and shared experimental inputs. Agreement with bound-state QED supports model-specific limits on additional interactions; it does not establish exact CPT symmetry or exclude every explanation of muon magnetic-moment measurements. A linked theoretical update reports a roughly 200 kHz disagreement between two predictions and explicitly leaves its origin unresolved; neither experiment resolves that difference at its stated precision.
Evidence
The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. These are related measurements with simulated trajectory-dependent line shapes, microwave-power corrections and residual excited-state contamination. The isolated transition offers a route to lower systematic error, while its reported statistical uncertainty is larger than that of the earlier measurement. The excited-state population and combined hyperfine interval are inferred through the stated model and shared experimental inputs. Agreement with bound-state QED supports model-specific limits on additional interactions; it does not establish exact CPT symmetry or exclude every explanation of muon magnetic-moment measurements. A linked theoretical update reports a roughly 200 kHz disagreement between two predictions and explicitly leaves its origin unresolved; neither experiment resolves that difference at its stated precision.
Contributors
- The named authors in the research record · SCIENCE: These 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.
- Precision measurement of the Lamb shift in Muonium (arXiv2108.12891v2)
- Measurement of the 2S1/2,F=0 to 2P1/2,F=1 transition in Muonium (arXiv2205.06202v1)
- Muonium Lamb shift: theory update and experimental prospects (arXiv2111.13951v1)
Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.
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