Measuring asymmetries in the decay of polarized neutrons with pNAB

Neutrons are a powerful tool to test fundamental symmetries of the weak interaction. Beta decay parameters like spin-momentum correlations and lifetime can determine the Vud parameter of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix and contribute to a test of its unitarity. The proposed pNAB experiment will use the Nab spectrometer at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source to measure electron and proton asymmetries in the decay of polarized neutrons with world-leading precision and has the potential to establish the neutron as the most precise probe of Vud and CKM unitarity.

This presentation will cover how the Nab spectrometer can be modified to achieve this goal, in particular how the neutron beam can be polarized with the required accuracy.