Characterization of the Energy Reconstruction Techniques Developed for the Large Silicon Detectors Used in the Nab Experiment

The Nab experiment is a neutron beta decay experiment designed to measure the decay angular correlation parameters to high precision, specifically: the electron-neutrino correlation (the "a" coefficient) and Fierz interference (the "b" coefficient). These measurements constrain potential new physics not incorporated in the Standard Model of particle physics. The experiment uses two large area highly segmented Si detectors to measure the decay protons and electrons in coincidence at either end of a solenoidal magnetic spectrometer. In order to achieve the aimed precision of Nab, the energy loss and performance of the detectors must be characterized to levels below the one percent level. Characterization of the energy response of the Nab detectors is presented here using techniques developed using multiple radioactive sources in conjunction with extensive simulations. To quantify the response of the detectors for a given pixel, the techniques used to define our energy calibration are presented, together with some details of the measured performance in both the Manitoba proton beam apparatus and the Nab spectrometer.