Searches for Exotic Spin-Dependent Interactions Through the Application of Slow Neutron Polarimetry

Exotic forces play an important role in the exploration of physics beyond the Standard Model. Neutron spin rotation provides a sensitive method in searches for interactions as shown in our measurements for the upper bound on parity-odd neutron interaction with ⁴He[1], possible long range spin-spin interactions[2], and exotic neutron spin-electron spin interactions within a compensated ferrimagnet[3]. Through the use of slow neutron polarimetry, we extend this technique in the measurement of exotic spin-dependent interactions between polarized neutrons and various sources. The NSR collaboration has employed both the Spallation Neutron Source and the High Flux Isotope Reactor at Oak Ridge National Lab for our experiments. We will discuss the theoretical background of our experiments and our ongoing preparations for improving future measurements.

[1] H. E. Swanson et al., Phys. Rev. C 100, 015204 (2019).

[2] C. Haddock et al., Phys. Lett. B 783, 227 (2018).

[3] C. D. Hughes et al., Journal of Magnetism and Magnetic Materials 629, 173273 (2025).