Three-Loop Corrections to Lamb Shift in Positronium: Electron Factor and Polarization

TL;DR

This paper calculates complex three-loop radiative corrections to positronium energy levels, advancing theoretical precision to match upcoming high-precision experimental measurements.

Contribution

It provides the first detailed calculation of three-loop corrections involving electron factors and polarization effects in positronium.

Findings

Calculated three-loop radiative contributions to positronium energy levels.

Enhanced theoretical accuracy for $meta^7$ order corrections.

Supports comparison with upcoming high-precision experiments.

Abstract

Hard spin-independent three-loop radiative contributions to energy levels in positronium generated by the two-photon-exchange diagrams with one-loop radiative insertions in the fermion lines and exchanged photons are calculated. This is a next step in calculations of all corrections of order $m\alpha^7$ inspired by the new generation of precise $1S-2S$ and $2S-2P$ measurements in positronium.