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A: Fachverband Atomphysik

A 42: Atomic Systems in External Fields II

A 42.6: Vortrag

Freitag, 6. März 2026, 12:15–12:30, N 3

Completed two-loop QED calculations for improving the bound-electron g-factor theory — •Bastian Sikora, Vladimir A. Yerokhin, Christoph H. Keitel, and Zoltan Harman — Max Planck Institute for Nuclear Physics, Heidelberg, Germany

The bound-electron g-factor in heavy hydrogenlike ions can be measured with extreme precision. However, the theoretical uncertainty of the g-factor is orders of magnitude larger than the experimental uncertainty in this regime, due to uncalculated QED binding corrections at the two-loop level. This was highlighted in a recent collaboration where experimental and theoretical g-factors of the hydrogenlike tin ion were compared [1].

Taking into account the electron-nucleus interaction exactly, we recently completed the computation of QED Feynman diagrams with two self-energy loops. In our new work, we demonstrate that our results lead to a significant improvement of the total theoretical uncertainty of the bound-electron g-factor in the high-Z regime [2].

Our calculations will enable improved tests of QED in planned near-future experiments with heavy hydrogenlike ions, e.g. at ALPHATRAP and ARTEMIS. Furthermore, our results are relevant for the determination of fundamental constants and nuclear parameters as well as searches for physics beyond the standard model using heavy ions.

[1] J. Morgner, B. Tu, C. M. König, et al., Nature 622, 53 (2023)

[2] B. Sikora, V. A. Yerokhin, C. H. Keitel and Z. Harman, Phys. Rev. Lett. 134, 123001 (2025)

Keywords: Zeeman effect; Bound-state QED; High-precision theory