Simulations of Electron Detection Systematic Errors for a UCNA+ Experiment

Research and Development towards UCNA+, an upgrade of the UCNA experiment, is underway at the LANSCE UCN facility. The UCNA experiment extracted the beta asymmetry, A₀, from polarized neutron decay. The angular correlation coefficient A₀ determines, λ, the ratio of the weak axial vector and vector coupling constants, g_A/g_V . In practice, A₀ is determined from the asymmetry in the number of counts in two detector systems, mounted at either end of a cylindrical decay cell with its symmetry axis aligned with the spectrometer magnetic field. In order to extract A₀ from the measured asymmetry we have investigated the effect of electron scattering. We present results from a Monte Carlo analysis of the UCNA+ experimental setup. We have modeled various possible geometries for thin foils in the experiment, such as the thickness of the decay trap endcap foils, foils encapsulating conversion electron sources, detector dead layers, etc. The goal of the simulations of these various geometries is to define a set of dedicated measurements that can be used to tune and benchmark the Monte Carlo beta scattering corrections to the asymmetry in a full UCNA+ experiment. Results from this work will be presented.