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DOE OSTI · 2474513

Muon spin force

Ema, Yohei·Gao, Ting·Pospelov, Maxim
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Abstract

Current discrepancy between the measurement and the prediction of the muon anomalous magnetic moment can be resolved in the presence of a long-range force created by ordinary atoms acting on the muon spin via axial-vector and/or pseudoscalar coupling, and requiring a tiny O⁡(10 –13 eV) spin energy splitting between muon state polarized in the vertical direction. We suggest that an extension of the muon spin resonance (μ⁢SR) experiments can provide a definitive test of this class of models. We also derive indirect constraints on the strength of the muon spin force by considering the muon-loop-induced interactions between nuclear spin and external directions. The limits on the muon spin force extracted from the comparison of 199 Hg/ 201 Hg and 129 Xe/ 131 Xe spin precession are strong for the pseudoscalar coupling but are significantly relaxed for the axial-vector one. These limits suffer from significant model uncertainties, poorly known proton/neutron spin content of these nuclei, and therefore do not exclude the possibility of a muon spin force relevant for the muon g – 2.

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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSHypothetical scalarsMagnetic momentMuon spin resonanceMuonsSpin dynamics

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Ema, Yohei, Gao, Ting, Pospelov, Maxim. 2024-10-21. Muon spin force. https://doi.org/10.1103/physrevd.110.075024

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