Impact of Lorentz violation on anomalous magnetic moments of charged leptons

Abstract

We address the question whether a violation of Lorentz symmetry can explain the tension between the measurement and the Standard-Model prediction of the anomalous magnetic moment of the muon ($(g-2)_{\mu}$) and whether it can significantly impact the one of the electron ($(g-2)_{e}$). While anisotropic Lorentz-violating effects are, in general, expected to produce sidereal oscillations in observables, isotropic Lorentz violation in the charged-lepton sector could feed into $(g-2)_{e,\mu}$. However, we find that this type of Lorentz violation, parametrised via a dim-4 field operator of the Standard-Model Extension (SME), is already strongly constrained by the absence of vacuum \v{C}erenkov radiation and photon decay. In particular, the observations of very-high-energetic astrophysical photons at LHAASO and of high-energetic electrons (muons) by the LHC (IceCube) place the most stringent two-sided bounds on the relevant SME coefficients $\overset{\circ}{c}{}^{(e)}$ ($\overset{\circ}{c}{}^{(\mu)}$). Therefore, any explanation of the tension in $(g-2)_{\mu}$ via isotropic Lorentz violation of the minimal spin-degenerate SME is excluded, and the possible size of its impact on $(g-2)_{e}$ is very limited.