Abstract
We provide an up to date summary of the theory contributions to the 2S → 2P Lamb shift and the fine structure of the 2P state in the muonic helium ion (μ4He)+. This summary serves as the basis for the extraction of the alpha particle charge radius from the muonic helium Lamb shift measurements at the Paul Scherrer Institute, Switzerland. Individual theory contributions needed for a charge radius extraction are compared and compiled into a consistent summary. The influence of the alpha particle charge distribution on the elastic two-photon exchange is studied to take into account possible model-dependencies of the energy levels on the electric form factor of the nucleus. We also discuss the theory uncertainty which enters the extraction of the 3He–4He isotope shift from the muonic measurements. The theory uncertainty of the extraction is much smaller than a present discrepancy between previous isotope shift measurements. This work completes our series of n=2 theory compilations in light muonic atoms which we have performed already for muonic hydrogen, deuterium, and helium-3 ions.
Original language | English |
---|---|
Pages (from-to) | 220-244 |
Number of pages | 25 |
Journal | Annals of Physics |
Volume | 396 |
DOIs | |
Publication status | Published - 1 Sept 2018 |
Funding
We thank E. Borie, A. P. Martynenko, S. Karshenboim, S. Bacca, N. Barnea, M. C. Birse, C. E. Carlson, M. I. Eides, J. Friar, M. Gorchtein, F. Hagelstein, O. J. Hernandez, U. Jentschura, C. Ji, J. A. McGovern, N. Nevo Dinur, C. Pachucki, V. Pascalutsa, and M. Vanderhaeghen for fruitful discussions in the creation of this summary. We specially thank A. P. Martynenko for providing the tools to repeat their calculation of the Friar moment, I. Sick for providing us with a sum of Gaussians FF parameterization of the world data from elastic electron scattering, and S. Bacca, N. Barnea, O. J. Hernandez, C. Ji, and N. Nevo Dinur for enlightening discussions regarding the TPE contribution and for making available to us their updated results ahead of publication. Weacknowledge support from the European Research Council (ERC) through StG. #279765 and CoG. #725039 , the Excellence Cluster PRISMA of the University of Mainz , and the Swiss National Science Foundation SNF , Project 200021_165854.
Funders | Funder number |
---|---|
Swiss National Science Foundation SNF | 200021_165854 |
University of Mainz | |
Horizon 2020 Framework Programme | 725039 |
European Research Council | StG. #279765 |
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung |
Keywords
- Fine structure
- Helium
- Isotope shift
- Lamb shift
- Muonic atoms/ions
- Nuclear structure