Pulse Shape Discrimination for the Nab Experiment

The Nab neutron beta decay correlation experiment will measure "a", the electron-neutrino correlation coefficient, and "b", the Fierz interference term. "a" serves as a test of CKM matrix unitarity while "b" places restrictions on the presence of scalar and tensor couplings in the weak interaction. These measurements will be done via detection of coincident protons and electrons with a pair of pixelated silicon detectors. The signals created by the incident particles vary in shape depending on parameters such as hit location within a pixel. Such variations can cause systematic shifts in timing and energy reconstruction. The Nab experiment precision goals necesitate understanding the mean timing bias to less than 1ns. A novel pulse shape discrimination technique has been developed utilizing GPUs to match waveforms to template shape functions to correct for biases in timing extraction from digitized signals. The effectiveness of this method at extracting proton hit locations from data collected at the University of Manitoba will be presented.