Non-relativistic contributions in order $\alpha^5m_\mu c^2$ to the Lamb shift in muonic hydrogen, deuterium and helium ion

Abstract

Contributions to the energy levels in light muonic atoms and, in particular, to the Lamb shift fall into a few well-distinguished classes. The related diagrams are calculated using different approaches. In particular, there is a specific kind of non-relativistic contributions. Here we consider such corrections to the Lamb shift in order $\alpha^5m_\mu$. These contributions are due to free vacuum polarization loops as well as to various effects of light-by-light scattering. The closed loop in the related diagrams is an electronic one, which allows a non-relativistic consideration of the muon. Both kinds of contributions have been known for a while, however, the results obtained up to date are only partial ones. We complete a calculation of the $\alpha^5m_\mu$ contributions for muonic hydrogen. The results are also adjusted for muonic deuterium and muonic helium ion.