Research and Development Goals for Angular Correlations Experiments with Ultracold Neutrons

Neutron decay correlation measurements provide a direct determination of the axial coupling constant of the nucleon, and play a central role in the high precision characterization of the charged weak interaction.  The upgraded ultracold neutron (UCN) source at the Los Alamos Neutron Science Center has created an opportunity for significant improvements in the sensitivity of decay correlation measurements with UCNs.  Although UCNs offer significant advantages with key sources of systematic error, the UCNA experiment is the only high precision angular correlation experiment which utilizes UCN, and determines the angular correlation between the neutron spin and the emitted beta particle.  Experience with the UCNA experiment has set the stage for upgrades to the experiment which can push the precision to between 0.2% and 0.1%.  The motivation and R&D goals identified to achieve a sensitivity below 0.2% for an upgrade of UCNA are presented, together with recent progress at Los Alamos.