Abstract
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 νHFS=4.463302(4)GHz was obtained with a relative precision of 0.9 ppm. The result was consistent with the previous ones obtained at Los Alamos National Laboratory and the current theoretical calculation. We present a demonstration of the microwave spectroscopy of muonium for future experiments to achieve the highest precision.
Highlights
Muonium (Mu) is a bound-state of a positive muon and an electron, which was discovered by V
Systems containing second-generation particles amenable to precise spectroscopy are very limited, and muonium plays a unique role in searches for physics beyond the standard model and tests of lepton universality
New precision measurement of the Mu hyperfine structure (HFS) using the high-intensity pulsed muon beam was performed at Japan Proton Accelerator Research Complex (J-PARC) Materials and Life Science Experimental Facility (MLF) Muon Science Establishment (MUSE)
Summary
Muonium (Mu) is a bound-state of a positive muon and an electron, which was discovered by V. One can obtain a more precise value of ∕ by comparing the theoretical prediction and the experimental result Since this indirectly obtained mass ratio has a much smaller relative uncertainty (20 ppb), it is used to evaluate physical quantities depending on ∕. Combining results of new measurements of Mu HFS and 1S-2S will provide one of the most stringent tests of bound-state QED, and one can extract the Rydberg constant without finite-size effects of a nucleus. Systems containing second-generation particles amenable to precise spectroscopy are very limited, and muonium plays a unique role in searches for physics beyond the standard model and tests of lepton universality. To exceed the limits of previous experiments and realize spectroscopy with higher precision, the MuSEUM collaboration proposed a new experiment using a high-intensity pulsed muon beam at J-PARC [27]. The novelty and significance of the experiment described in this paper are the high-intensity pulsed muon beam’s application to precise spectroscopy using a high-rate capable particle detector
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