Monte Carlo Simulations in the BL3 Experiment

Neutron beta decay is a fundamental process in nuclear physics that provides sensitive means to uncover the details of the weak interaction. A precise measurement of the neutron lifetime, along with neutron beta decay correlations, can provide tests of CKM unitarity and is needed for Big Bang Nucleosynthesis calculations of the primordial $^4$He abundance, which correlates with other cosmological parameters. A next generation beam method experiment, BL3 at the NCNR, aims to improve the systematic precision of neutron lifetime measurements in order to resolve the discrepancy between beam and bottle method measurements. In BL3, the recoil protons from neutron beta decay are born in a quasi-Penning trap with magnetic and electric fields that transport them to a segmented silicon detector. The BL3 experiment will use higher neutron flux in a larger beam, which necessitates a new, large, pixelated proton detector. The BL3 collaboration is using a combination of simulation tools to assess systematic effects and the anticipated performance of the apparatus. We will present Monte Carlo simulations of neutron beam studies and decay proton transportation from the trap to the silicon detector.