An Improved Experimental Limit on the Electric Dipole Moment of the Neutron

TL;DR

This paper reports a highly sensitive experimental search for the neutron's electric dipole moment, setting a new upper limit that constrains theories beyond the Standard Model of particle physics.

Contribution

The study introduces improved techniques to suppress magnetic noise and systematically analyze false signals, resulting in a more stringent upper limit on the neutron EDM.

Findings

Upper limit on neutron EDM: |d_n| < 2.9 x 10^{-26} e cm at 90% CL

Reduction of magnetic-field fluctuation effects using a mercury magnetometer

Careful analysis of systematic uncertainties and false signals

Abstract

An experimental search for an electric-dipole moment (EDM) of the neutron has been carried out at the Institut Laue-Langevin (ILL), Grenoble. Spurious signals from magnetic-field fluctuations were reduced to insignificance by the use of a cohabiting atomic-mercury magnetometer. Systematic uncertainties, including geometric-phase-induced false EDMs, have been carefully studied. Two independent approaches to the analysis have been adopted. The overall results may be interpreted as an upper limit on the absolute value of the neutron EDM of |d_n| < 2.9 x 10^{-26} e cm (90% CL).