Characterization Studies of Nab’s Silicon Detectors through simulation

The Nab Experiment, hosted at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, intends to use the decay of unpolarized free neutrons to test the Standard Model (SM) and search for beyond SM physics. In particular, the experiment is designed to probe the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix and search for scalar and tensor couplings in the Weak Interaction, through precise measurement of the electron-neutrino correlation coefficient, a (△a/|a| = 10^-3), and the Fierz Interference term, b (△b = 3*10^-3).

Located at either end of the spectrometer, highly pixelated Si detectors measure neutron beta decay particle energies. We simulate the decay particles paths and energies using Geant4, to serve as a test bed for analysis tools and to accurately model the experiment.

This poster presents simulations of the effects of the detector response to decay particles. This includes the development of Geant4 macros that output energy deposition as a function of particle type, incident energy, impact angle, and choice of underlying physics list. The simulated data is used to simulate pulse shape with the tools developed by the Nab Experiment Shape Simulation Effort (NESSIE). The ultimate aim is to create a simulated database that sufficiently characterizes detector response across various parameters that can be called upon when analyzing production data.