Improved Bound-Electron g-Factor Theory through Complete Two-Loop QED Calculations

Abstract:

The two-loop self-energy correction to the bound-electron 𝑔 factor in hydrogenlike ions is investigated, taking into account the electron-nucleus interaction exactly. This all-order calculation is required to improve the total theoretical uncertainty of the 𝑔 factor, which is limited by the fact that two-loop self-energy corrections have only been calculated so far in the form of an expansion in 𝑍⁢𝛼. Here, 𝑍 is the nuclear charge number and 𝛼 is the fine-structure constant. In this work, we report calculations of the last missing parts of the total two-loop self-energy correction, exactly in 𝑍⁢𝛼. We apply our theory to the recently measured 𝑔 factor of the hydrogenlike 118Sn49+ ion [J. Morgner et al., Nature (London) 622, 53 (2023)] and, with a factor of 8, improve the accuracy of its state-of-the-art theoretical value by almost one order of magnitude, enabling more detailed tests of quantum electrodynamics and new physics in strong fields.

B. Sikora, V. A. Yerokhin, C. H. Keitel, Z. Harman, „Improved Bound-Electron g-Factor Theory
through Complete Two-Loop QED Calculations“, Phys. Rev. Lett. 134, 123001 (2025).

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.123001

Related to Project B02