New Muonic Helium Atom HFS Measurements at J-PARC MUSE
ORAL
Abstract
Muonic helium (μHe) is a hydrogen-like atom composed of a helium atom with one of its
electrons replaced by a negative muon. Its ground-state hyperfine structure (HFS), from the
interaction of the remaining electron and the negative muon magnetic moment, is very similar
to muonium (bound state of a positive muon and an electron). Measurements of the μHe-
HFS interval are a sensitive tool to test the three-body atomic system, bound-state quantum
electrodynamics (QED) theory, and determine fundamental constants of the negative muon
magnetic moment and mass. We can verify the CPT symmetry in muons by comparing these
constants with positive muons.
Precise measurements of the muonium ground-state HFS interval using a microwave
magnetic resonance technique are now in progress at J-PARC by the MuSEUM collaboration.
The same method can be used to precisely determine the μHe-HFS and the negative muon
magnetic moment and mass.
We have successfully measured μHe-HFS at zero field using CH4 as an electron donor at J-
PARC MUSE D-line with better accuracy than previous studies. We are now planning high-
field measurements using the world's most intense pulsed negative muon beam at MUSE
and muon repolarization by SEOP technique. The latest results and future plans will be
outlined.
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Publication: [1]P. Strasser et al., J. Phys.: Conf. Ser. 2462, 012023 (2023)
[2]P. Strasser et al., https://arxiv.org/abs/2306.07533
Presenters
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Yu Goto