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 x 10(-26)e cm (90% C.L.).

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; 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 n ¼ −0.21 AE 1.82 × 10 −26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0 × 10 −26 e cm (90% C.L.) or 3.6 × 10 −26 e cm (95% C.L.).

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We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating timereversal invariance. The salient features of this experiment were the use of a 199 Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d n ¼ ð0.0 AE 1.1 stat AE 0.2 sys Þ × 10 −26 e:cm.

A combined fit is presented to data onpp annihilation in flight to final states ηπ 0 π 0 , π 0 π 0 , ηη, ηη and π − π + . The emphasis lies in improving an earlier study of ηπ 0 π 0 by fitting data at ninep momenta simultaneously and with parameters consistent with the two-body channels. There is evidence for all of the I = 0, C = +1qq states expected in this mass range. New resonances are reported with masses and widths (M, Γ) as follows: J PC = 4 −+ (2328 ± 38, Γ = 240 ± 90) MeV, 1 ++ (1971 ± 15, 240 ± 45) MeV, 0 −+ (2285 ± 20, 325 ± 30) MeV, and 0 −+ (2010 +35 −60 , 270 ± 60) MeV. Errors on the masses and widths of other resonances are also reduced substantially. All states lie close to parallel straight line trajectories of excitation number v. mass squared.