Positronium energy levels at order $m{\alpha }^7$: vacuum polarization corrections in the two-photon-annihilation channel

Abstract

We have calculated all contributions to the energy levels of parapositronium at order $m{\alpha }^7$ coming from vacuum polarization corrections to processes involving virtual annihilation to two photons. This work is motivated by ongoing efforts to improve the experimental determination of the positronium ground-state hyperfine splitting.

Comments: 6 pages, 2 figures