First Observation of Cyclotron Radiation from MeV-Scale e^{±} following Nuclear β Decay.

We present an apparatus for detection of cyclotron radiation yielding a frequency-based β^{±} kinetic energy determination in the 5 keV to 2.1 MeV range, characteristic of nuclear β decays. The cyclotron frequency of the radiating β particles in a magnetic field is used to determine the β energy precisely.

Neutron Polarimetry Using a Polarized He Cell for the aCORN Experiment.

The neutron polarization of the NG-C beamline at the NIST Center for Neutron Research was measured as part of the aCORN neutron beta decay experiment. Neutron transmission through a polarized He spin filter cell was recorded while adiabatic fast passage (AFP) nuclear magnetic resonance (NMR) reversed the polarization direction of the He in an eight-step sequence to account for drifts. The dependence of the neutron transmission on the spin filter direction was used to calculate the neutron polarization.

Precision Measurement of the Neutron Scattering Length of ^{4}He Using Neutron Interferometry.

We report a 0.08% measurement of the bound neutron scattering length of ^{4}He using neutron interferometry. The result is b=(3.

Progress on the BL2 beam measurement of the neutron lifetime.

A precise value of the neutron lifetime is important in several areas of physics, including determinations of the quark-mixing matrix element │ │, related tests of the Standard Model, and predictions of light element abundances in Big Bang Nucleosynthesis models. We report the progress on a new measurement of the neutron lifetime utilizing the cold neutron beam technique. Several experimental improvements in both neutron and proton counting that have been developed over the last decade are presented.

Measurement of the Electron-Antineutrino Angular Correlation in Neutron β Decay.

We report the first result for the electron-antineutrino angular correlation (a coefficient) in free neutron β decay from the aCORN experiment. aCORN uses a novel method in which the a coefficient is proportional to an asymmetry in proton time of flight for events where the β electron and recoil proton are detected in delayed coincidence. Data are presented from a 15 month run at the NIST Center for Neutron Research.