New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam

Understand

A hydrogen-like atom consisting of a positive muon and an electron is known as muonium.

• It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries.
• The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter.
• The resonance of hyperfine transition was successfully observed at a near-zero magnetic field, and the muonium hyperfine structure interval of ${\nu}_{\text{HFS}}$ = 4.463302(4) GHz was obtained with a relative precision of 0.9 ppm.