Simulation of the Effect of the Proton Hit Energy Threshold on Proton Efficiency in the Nab Experiment

The Nab experiment, located at the Spallation Neutron Source in Oak Ridge National Laboratory, will measure the electron-neutrino coefficient 'a', and the Fierz interference parameter 'b' in unpolarized neutron beta decay to test the unitarity of the Cabibbo-Kobayashi-Maskawa matrix and search for physics beyond the Standard Model. An asymmetric spectrometer is used to guide protons and electrons from the decay point in a non-uniform magnetic field to two silicon detectors, which measure the electron energy and proton time-of-flight. Simulations of the experiment in GEANT4 are used to develop the analysis procedure and understand systematic uncertainties. In this poster, I show the effects of proton efficiency on the upper detector at different energy thresholds using simulated data from Geant4. The proton energy spectra is used to determine these efficiencies. This project aims to determine a low enough threshold for protons and electrons hitting the detectors such that the bias in the determination of the 'a' coefficient is acceptable. I also discuss whether the adiabatic approximation is valid for protons and electrons traveling toward the upper detector, giving further insight on the detection efficiency and how it affects the uncertainty of the a coefficient