Improved Experimental Limit on the Electric Dipole Moment of the Neutron

TLDR

An experiment at the Institut Laue‑Langevin measured the neutron EDM using a cohabiting atomic‑mercury magnetometer to suppress magnetic‑field fluctuations and carefully studied systematic uncertainties such as geometric‑phase false EDMs. The experiment sets a 90 % confidence upper limit of |d_n| < 2.9 × 10^−26 e cm on the neutron electric dipole moment.

Abstract

An experimental search for an electric dipole moment (EDM) of the neutron has been carried out at the Institut Laue-Langevin, 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. The results may be interpreted as an upper limit on the neutron EDM of $|{d}_{n}|<2.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}e\text{ }\text{ }\mathrm{cm}$ (90% C.L.).