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

Abstract

High precision measurements of the ground state hyperfine structure (HFS) of muonium 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. Previous measurements were performed decades ago at LAMPF with uncertainties mostly dominated by statistical errors. At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planning complementary measurements of muonium HFS both at zero and high magnetic field. The new high-intensity muon beam that will soon be available at H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. 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 results at zero field are presented.

Intense beam of metastable Muonium

“…A future precision measurement using a CW laser is planned by the Mu-MASS experiment [14]. The measurement of the ground-state hyperfine structure currently determines the muon magnetic moment with the highest precision [15], with an improvement underway by the MUSEUM collaboration [16,17]. However, the methods used for M production in these measurements do not produce sufficient M(2S) in vacuum, and so cannot be used to study transitions from long-lived excited states.…”

Muon g-2 and EDM experiments as muonic dark matter detectors

“…The final precision is expected to be similar to that of Fermilab and BNL, 0.5 ppm on a µ and |d µ | 2 • 10 −21 e • cm. In addition, J-PARC is planning to perform new measurements of muonium spectroscopy using their muon source [33] which may be used to deduce a µ from the g-2 data.…”

Overview of the Phenomenology of Lorentz and CPT Violation in Atomic Systems

“…Finally, the best bounds on the muon nonrelativistic coefficients were obtained from hyperfine transitions of the ground state of muonium and the 1 s-2 s transition in muonium [17,34,47]; see Tables 3 and 5. The reader should be aware that many of the bounds reported in [34][35][36] have not been reproduced in this section.…”