Revised value of the eighth-order QED contribution to the anomalous magnetic moment of the electron

TL;DR

This paper presents a revised calculation of the eighth-order quantum electrodynamics contribution to the electron's magnetic moment, correcting previous inconsistencies and refining the value of the fine structure constant.

Contribution

It introduces a new evaluation method using an automatic code generator and corrects prior infrared divergence treatment errors, providing a more accurate eighth-order QED contribution.

Findings

Revised eighth-order QED contribution: 1.15965218279(7.71) x 10^{-12}

Updated fine structure constant: alpha^{-1} = 137.035999084(51)

Improved agreement between theory and experiment

Abstract

We have carried out a new evaluation of the eighth-order contribution to the electron g-2 using FORTRAN codes generated by an automatic code generator gencodeN. Comparison of the "new" result with the "old" one has revealed an inconsistency in the treatment of the infrared divergences in the latter. With this error corrected we now have two independent determinations of the eighth-order term. This leads to the revised value 1 159 652 182.79 (7.71) x 10^{-12} of the electron g-2, where the uncertainty comes mostly from that of the best non-QED value of the fine structure constant alpha. The new value of alpha derived from the revised theory and the latest experiment is alpha^{-1} = 137.035 999 084 (51) [0.37 ppb], which is about 4.7 ppb smaller than the previous alpha^{-1}.