QED with heavy ions: on the way from strong to supercritical fields

TL;DR

This paper reviews experimental and theoretical progress in testing quantum electrodynamics with heavy ions, focusing on supercritical fields, pair creation, and fundamental constant determination, highlighting recent achievements and future research directions.

Contribution

It provides a comprehensive overview of QED tests in heavy-ion collisions, emphasizing supercritical regimes and the observation of vacuum decay phenomena.

Findings

Agreement between theory and experiment for Lamb shift and hyperfine splitting

Potential observation of spontaneous pair creation in supercritical fields

Advances in measuring the $g$ factor in highly charged ions

Abstract

The current status of tests of quantum electrodynamics with heavy ions is reviewed. The theoretical predictions for the Lamb shift and the hyperfine splitting in heavy ions are compared with available experimental data. Recent achievements and future prospects in studies of the $g$ factor with highly charged ions are also reported. These studies can provide precise determination of the fundamental constants and tests of QED within and beyond the Furry picture at the strong-coupling regime. Theoretical calculations of the electron-positron pair creation probabilities in low-energy heavy-ion collisions are also considered. Special attention is paid to tests of QED in supercritical-field regime, which can be accessed in slow collisions of two bare nuclei with the total charge number larger than the critical value, $Z_{\rm crit} \approx 173$. In the supercritical field, the initially neutral vacuum can spontaneously decay into the charged vacuum and two positrons. It is demonstrated that this fundamental phenomenon can be observed via impact-sensitive measurements of the pair-production probabilities.