New Experimental Limit on the Electric Dipole Moment of the Neutron

Abstract

The latest neutron electric dipole moment (EDM) experiment has been collecting data at the Institut Laue-Langevin (ILL), Grenoble, since 1996. It uses an atomic-mercury magnetometer to compensate for the magnetic field fluctuations that were the principal source of systematic errors in previous experiments. The first results, in combination with the previous ILL measurement, yield a possible range of values of $(-7.0<d_n<5.0\mathrm{})\times {10}^{-26\mathrm{}}e\mathrm{cm}$ ( $90\%$ C.L.). This may be interpreted as an upper limit on the absolute value of the neutron EDM of $|d_n|<6.3\mathrm{}\times {10}^{-26\mathrm{}}e\mathrm{cm}$ ( $90\%$ C.L.).