An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
C. A. Baker, D. D. Doyle, P. Geltenbort, K. Green, M. G. D. van der Grinten, P. G. Harris, P. Iaydjiev, S. N. Ivanov, D. J. R. May, J. M. Pendlebury, J. D. Richardson, D. Shiers, K. F. Smith
TL;DR
The study reports an improved experimental limit on the neutron electric dipole moment using a cohabiting mercury magnetometer to suppress magnetic-field fluctuations. It provides a thorough analysis of geometric-phase effects and a wide range of systematic uncertainties, including light shifts and HV-related factors. Two independent analyses yield a final 90% credibility upper limit of |d_n| < 2.9×10^-26 e cm, consistent with prior limits but with a more complete error accounting. The work consolidates neutron EDM data from 1998–2002 and strengthens constraints on CP-violating physics beyond the Standard Model.
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).