Two selected examples from low energy / high precision particle physics: searching for axion-like particles with stored neutrons & laser spectroscopy of light muonic atoms

​Particle physics is often related with high energy collider experiments. However, there are various other methods to perform high precision experiments at low energies or high intensities which test fundamental symmetries, interactions or other properties described in the Standard model or also beyond.

One possible example is clock comparisons. In an experiment performed by the nEDM collaboration, the Larmor precession frequencies of stored neutrons and cohabiting 199Hg atoms were compared precisely. Such a measurement allows to investigate possible short range spin-dependent interactions which could be mediated by axions or axion-like particles. This is of particular interest because their interaction strength is proportional to the CP-violating product of scalar and pseudoscalar coupling constants gSgP.

Another example, which brings atomic physics and particle physics techniques together, is the spectroscopy of light muonic atoms or ions. Those bound systems of a nucleus and a muon have an increased sensitivity on finite size effects of the nucleus due to the ~200-fold mass of the muon compared to the electron.

The CREMA collaboration has measured the Lamb shift in muonic hydrogen and muonic deuterium atoms, as well as in muonic helium-4 and helium-3 ions -- which allows to determine charge radii and other nuclear properties with improved precision compared to previously conducted measurements. During my presentation I would like to introduce these two experiments and point out my contributions to the achieved results.