Muon spin force

Journal Article · 21 October 2024 · Physical Review. D.

DOI: https://doi.org/10.1103/PhysRevD.110.075024 · OSTI ID:2474513

Ema, Yohei; Gao, Ting; Pospelov, Maxim

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 $\mathcal{O}\left({10}^{-13}\mathrm{eV}\right)$ spin energy splitting between muon state polarized in the vertical direction. We suggest that an extension of the muon spin resonance ( $\mathrm{\mu }\mathrm{SR}$ ) 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 ${}^{199}\mathrm{Hg}/{}^{201}\mathrm{Hg}$ and ${}^{129}\mathrm{Xe}/{}^{131}\mathrm{Xe}$ 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 $g-2$ . Published by the American Physical Society 2024

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0011842
• OSTI ID: 2474513
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 7 Vol. 110; ISSN PRVDAQ; ISSN 2470-0010
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English