A Revised Experimental Upper Limit on the Electric Dipole Moment of the Neutron

TL;DR

This paper provides a detailed reanalysis of experimental data to establish a more precise upper limit on the neutron's electric dipole moment, incorporating recent systematic error considerations.

Contribution

It offers a comprehensive re-evaluation of neutron EDM measurements with improved analysis techniques and updated systematic error estimates.

Findings

Revised upper limit on neutron EDM: 3.0 × 10^{-26} ecm (90% CL)

Enhanced understanding of gravity effects in ultracold neutrons

Consistent systematic error estimates with recent measurements

Abstract

We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons (UCN); an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of $d_\mathrm{n} = -0.21 \pm 1.82 \times10^{-26}$ $e$cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of $3.0 \times10^{-26}$ $e$cm (90% CL) or $ 3.6 \times10^{-26}$ $e$cm (95% CL). This paper is dedicated by the remaining authors to the memory of Prof. J. Michael Pendlebury.