https://doi.org/10.1140/epjd/s10053-023-00639-z
Regular Article – Atomic Physics
Update of Muonium 1S–2S transition frequency
1
Institute for Particle Physics and Astrophysics, ETH, 8093, Zurich, Switzerland
2
Paul Scherrer Institute, PSI, 5232, Villigen, Switzerland
3
P.N. Lebedev Physical Institute, 119991, Moscow, Russia
Received:
7
February
2023
Accepted:
20
March
2023
Published online:
19
April
2023
We present an updated value of the Muonium 1S–2S transition frequency, highlighting contributions from different QED corrections as well as the large uncertainty in the Dirac contribution, stemming from the uncertainty of the electron to muon mass ratio. Improving the measurement of this spectral line would allow to extract a more accurate determination of fundamental constants, such as the electron to muon mass ratio or, combined with the Muonium hyperfine splitting, an independent value of the Rydberg constant. Furthermore, we report on the current status of the Mu-MASS experiment, which aims at measuring the Muonium 1S–2S transition frequency at a 
uncertainty level.
© The Author(s) 2023
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