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This article describes measurements of angular-correlation coefficients in the decay of free neutrons with the superconducting spectrometer PERKEO II. A method for measuring the β-asymmetry coefficient A is presented, as well as a new method for determining the neutrino-asymmetry coefficient B, which allows a value for the proton-asymmetry coefficient C to… (More)
A new measurement of the neutrino asymmetry parameter B in neutron decay, the angular correlation between neutron spin and antineutrino momentum, is presented. The result, B=0.9802(50), confirms earlier measurements but features considerably smaller corrections. It agrees with the standard model expectation and permits updated tests on "new physics" in… (More)
We present a first experimental demonstration of a new method to extract a well-collimated beam of ultra-cold neutrons (UCN) from a storage vessel. Neutrons with too large divergence are not removed from the beam by an absorbing collimation, but a diffuse or semidiffuse channel with high Fermi potential reflects them back into the vessel. This avoids… (More)
Time reversal invariance violation beyond the Standard model mechanism can be tested in free neutron beta decay. The triple correlation between neutron spin and the momenta of electron and antineutrino (D coefficient) tests T violating phases in non-standard couplings. We present a new preliminary limit for this correlation which was obtained by the Trine… (More)
We present the status of the development of a dedicated high density ultra-cold neutron (UCN) source dedicated to the gravitational spectrometer GRANIT. The source employs superthermal conversion of cold neutrons to UCN in superfluid helium. Tests have shown that UCN produced inside the liquid can be extracted into vacuum. Furthermore a dedicated neutron… (More)
The proton asymmetry parameter C in neutron decay describes the angular correlation between neutron spin and proton momentum. In this Letter, the first measurement of this quantity is presented. The result C= -0.2377(26) agrees with the standard model expectation. The coefficient C provides an additional parameter for new and improved standard model tests.
The neutron is a well-suited system to search for a violation of time reversal invariance beyond the Standard Model. Recent experiments and projects searching for time reversal violation in the neutron decay and in the neutron electric dipole moment will be presented.
We report on a new measurement of the neutron β-asymmetry parameter A with the instrument Perkeo II. The main enhancements are the high neutron polarization of P = 99.7(1)% from a novel arrangement of supermirror polarizers and reduced background from improvements in beam line and shielding. The leading corrections were thus reduced by a factor of 4,… (More)
We have observed depolarization effects when high intensity cold neutron beams are incident on alkali-metal spin-exchange-polarized 3He cells used as neutron spin filters. This was first observed as a reduction of the maximum attainable 3He polarization and was attributed to a decrease of alkali-metal polarization, which led us to directly measure… (More)
The combination of the intense cold neutron beam available at the PF1b beam position of the Institute Laue-Langevin (ILL) in Grenoble, together with the high detection efficiency of a large array of high purity Ge detectors (HPGe) has offered a unique opportunity for a set of experiments devoted to nuclear spectroscopy on stable isotopes as well as on… (More)