Simulations of Electron Detection Systematic Errors for the UCNA+ Experiment

The Ultracold Neutron Asymmetry UCNA+ experiment at Los Alamos National Laboratory is an upgrade to the original UCNA experiment which used polarized ultracold neutrons (UCN) to extract the electron asymmetry from neutron beta decay. The Asymmetry parameter, A₀, is the angular correlation between the neutron spin and the direction of the momentum of the decay electron. The angular correlation coefficient A₀ determines the ratio of the weak axial-vector and vector coupling constants, g_A/g_V . The UCNA experiment measured the coefficient A₀ to a precision of 0.60% using a 2 × 2π magnetic spectrometer. Upgrades to several subsystems are being considered, including the electron detection system. We present an exploratory Monte Carlo analysis of the UCNA+ experimental setup. We have simulated different experimental geometries in an effort to explore systematic uncertainty arising primarily from beta particles scattering from the trap endcap foils and detectors. One of the goals of this work is to identify a set of calibration measurements that can benchmark the modeling precision for scattering effects in the upgraded experiment. Results from these simulations will be discussed.