Searches for Exotic Spin-Dependent Interactions of Slow Neutrons with Matter using Neutron Spin Rotation

Polarized slow neutrons can be used to conduct sensitive searches for subtle spin-dependent neutron interactions in matter. A brief overview of the theoretical context in which such searches are important is given. We present the result of a recent measurement of neutron spin rotation in liquid helium that constrains possible exotic long-range parity-odd interactions between the neutron and matter from the exchange of spin 1 bosons of meV-scale masses. The experiment also places the first upper bound to our knowledge on what may be called “in-matter”gravitational torsion. Finally, we discuss a proposed search for a possible parity-even exotic interaction of polarized neutrons with matter from spin 1 boson exchange with axial couplings for boson masses in the meV range.