A robust limit for the electric dipole moment of the electron

TL;DR

This paper presents a more reliable and conservative bound on the electron's electric dipole moment by accounting for theoretical uncertainties and cancellations, improving the interpretation of experimental data in the search for new physics.

Contribution

It introduces an improved extraction method for the electron EDM that incorporates uncertainties and cancellations, providing a more robust bound than previous estimates.

Findings

The 95% C.L. upper bound on |d_e| is 0.14×10^{-26} e·cm.

The bound is comparable to previous results but derived more conservatively.

Prospects for improved bounds using other paramagnetic systems are analyzed.

Abstract

Electric dipole moments constitute a competitive method to search for new physics, being particularly sensitive to new CP-violating phases. Given the experimental and theoretical progress in this field and more generally in particle physics, the necessity for more reliable bounds than the ones usually employed emerges. We therefore propose an improved extraction of the electric dipole moment of the electron and the relevant coefficient of the electron-nucleon coupling, taking into account theoretical uncertainties and possible cancellations, to be used in model-dependent analyses. Specifically, we obtain at 95% C.L. |d_e|<=0.14 10^{-26}e cm with present data, which is very similar to the bound typically quoted from the YbF molecule, but obtained in a more conservative manner. We examine furthermore in detail the prospects for improvements and derive upper limits for the dipole moments of several paramagnetic systems presently under investigation, i.e. Cesium, Rubidium and Francium.