New precise measurements of muonium hyperfine structure at J-PARC MUSE

High precision measurements of the ground state hyperfine structure (HFS) of muonium, a leptonic system made of a bound state of a positive muon with an electron, is a stringent tool for testing bound-state quantum... [ view full abstract ]

High precision measurements of the ground state hyperfine structure (HFS) of muonium, a leptonic system made of a bound state of a positive muon with an electron, is a stringent tool for testing bound-state quantum electrodynamics (QED) theory, determining fundamental constants of the muon magnetic moment and mass, and searches for new physics. Muonium is the most suitable system to test QED because both theoretical and experimental values can be precisely determined.
At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planing complementary measurements of muonium HFS both at zero field and at high magnetic field. The new high-intensity muon beam that will soon be available at MUSE H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. The previous measurements at zero field [1] and high field [2] were performed decades ago at LAMPF with experimental uncertainties mostly dominated by statistical errors. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation for high-field measurements, and the latest measurements at zero field will be presented.

[1] D. E. Casperson et al., Physics Letters 59B (1975) 397.
[2] W. Liu et al., Physical Review Letters 82 (1999) 711.

Note: Contribution on behalf of the MuSEUM collaboration.