Precision pulse shape modeling for the Nab experiment

The Nab experiment at the Spallation Neutron Source aims to measure the electron-antineutrino correlation and Fierz interference term following neutron beta decay at the few $10^{-3}$ level, thereby probing exotic electroweak scalar and tensor currents at the TeV scale and providing crucial input for top-row CKM unitarity tests. Detection of protons and electrons is performed using large diameter, highly segmented silicon detectors at either side of the decay volume inside a magnetic spectrometer, and excellent reconstruction of both energy and timing is paramount. Per-segment determinations of both quantities depend on parameters which are either theoretically or empirically difficult to quantify, such as local impurity and trapping center concentrations, charge collection efficiency near the surface, plasma column dynamics and segment-to-segment insulation technology. We will report on a novel, consistent simulation and modeling effort for realistic pulse shape generation in silicon following low energy particle interaction, and discuss related systematic effects in the Nab experiment.