Speaker
Dr
Zoltán Harman
(Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany)
Description
Quantum electrodynamic (QED) effects in strong fields can be scrutinized to high precision in Penning trap experiments: a recent measurement yielded a value
for the $g$-factor of hydrogenlike silicon with a $5 \times 10^{-10}$ fractional uncertainty, allowing to test certain higher-order QED corrections for the
first time [1]. The measured $g$-factor is in excellent agreement with the state-of-the-art theoretical value, which includes QED contributions up to the two-loop level of the order of $(Z\alpha)^2$ and $(Z\alpha)^4$. At the above experimental accuracy, also nuclear structural effects start to be visible. We determined the nuclear root-mean-square radius of ${}^{28}$Si from the comparison of experimental and theoretical $g$-factors and found agreement to tabulated values within our limits of error [1]. As a further nuclear contribution, we investigated the influence of nuclear
deformation, and found the leading correction to become significant for mid-$Z$ ions and for very heavy elements to even reach the 10${}^{-6}$
level [2].
Furthermore, we present theoretical results of a recent determination of the electron mass via measurement of the Larmor and cyclotron frequencies in a ${}^{12}$C${}^{5+}$ ion confined in a Penning trap [3]. The electron mass was determined with a relative uncertainty more than an order of magnitude better than the established literature value by means of comparison of the theoretical prediction for $g \left( {}^{12}{\mathrm C}^{5+} \right)$ and the experimental frequencies. In order to reduce the uncertainty on the theory's side, the unknown two-loop higher-order correction to $g \left( {}^{12}{\mathrm C}^{5+} \right)$ was estimated. The electron mass is closely linked to other fundamental constants, such as the Rydberg constant $R_{\infty}$ and the fine-structure constant $\alpha$. Thus the current improvement of its value paves the way for future fundamental physics experiments and further precision tests of the Standard Model.
[1] S. Sturm, A. Wagner, B. Schabinger, J. Zatorski, Z. Harman, W. Quint, G. Werth, C. H. Keitel, K. Blaum, Phys. Rev. Lett. 107, 023002 (2011).
[2] J. Zatorski, N. Oreshkina, C. H. Keitel, Z. Harman, Phys. Rev. Lett. 108, 063005 (2012).
[3] S. Sturm, F. Köhler, J. Zatorski, A. Wagner, Z. Harman, G. Werth, W. Quint, C. H. Keitel, K. Blaum, Nature 506, 467 (2014).
Primary author
Dr
Zoltán Harman
(Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany)
Co-authors
Prof.
Christoph H. Keitel
(Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany)
Dr
Jacek Zatorski
(Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany)
