Hadronic vacuum polarization and the Lamb shift

Abstract

Recent improvements in the determination of the running of the fine-structure constant also allow an update of the hadronic vacuum-polarization contribution to the Lamb shift. We find a shift of $-$3.40(7) kHz to the $1S$ level of hydrogen. We also comment on the contribution of this effect to the determination by elastic electron scattering of the rms radii of nuclei.