A Search for Possible Long Range Spin Dependent Interactions of the Neutron From Exotic Vector Boson Exchange

TL;DR

This study searches for long-range spin-dependent interactions of neutrons mediated by hypothetical vector bosons, using polarized neutrons passing through matter, and sets new stringent limits on such interactions.

Contribution

It provides the first experimental constraints on neutron spin-dependent interactions mediated by axial vector bosons in the millimeter to micrometer range.

Findings

No significant spin-dependent interaction detected.

Improved upper bounds on neutron-matter coupling by three orders of magnitude.

Constraints applicable to theories extending the Standard Model.

Abstract

We present a search for possible spin dependent interactions of the neutron with matter through exchange of spin 1 bosons with axial vector couplings as envisioned in possible extensions of the Standard Model. This was sought using a slow neutron polarimeter that passed transversely polarized slow neutrons by unpolarized slabs of material arranged so that this interaction would tilt the plane of polarization and develop a component along the neutron momentum. The result for the rotation angle, $\phi'_{V_5} = [2.8\pm\,4.6(stat.)\pm\,4.0(sys.)]\times 10^{-5}~\mbox{rad/m}$ is consistent with zero. This result improves the upper bounds on the neutron-matter coupling $g_{A}^{2}$ from such an interaction by about three orders of magnitude for force ranges in the mm-$\mu$m regime.