Simulations of Neutron Spin Rotation Measurements by the NSR Collaboration

The Neutron Spin Rotation (NSR) Collaboration seeks to constrain the hadronic weak interaction as well as place limits on the possibility of long-range spin-dependent forces [1,2,3]. The NSR polarimeter is capable of measuring rotations on the order of 10^-7 radians per meter of target material. As transversely polarized neutrons pass through a pair of 0.5-m liquid Helium targets, the weak interaction causes minute rotations of the neutron spin about the longitudinal axis. Similarly, transversely polarized neutrons can tip forward due to a spin-dependent long-range force as they pass between different-mass plates. For the latter experiment, our target consists of a series of 0.5-m long glass and tungsten plates and can accept a 10 by 10-cm beam. The primary challenge of these high-precision measurements is the suppression of and cancellation of rotations due to the interaction of the neutron spin with ambient magnetic fields. Computer simulations of these experiments have proved a valuable tool in investigating the size of these affects and how to mitigate them. Discussion of recent simulation work will be presented.