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

We sought for a possible new axial vector interaction with a range in the millimeter to micron range using spin dependent interactions of neutrons with matter though exchange of spin 1 bosons as predicted in some extensions of the Standard Model.  This experiment was performed on FP12 at the LANSCE facility at Los Alamos by sending transversely polarized slow neutrons through gaps near slabs of copper and float glass arranged so that the possible exotic interaction would tilt the plane of polarization along the neutron momentum [3]. The resulting rotation angle φ′ =[2.8±4.6(stat.)±4.0(sys.)]×10⁻⁵rad/m was consistent with zero [1]. The upper bound on an exotic axial vector neutron-matter coupling g²_A was improved by about three orders of magnitude for force ranges in the mm-μm [2]. We discuss this result along with our plan to further improve the sensitivity of our search by at least 2 orders of magnitude at the NIST NG-C beam using tungsten slabs as the source.

[1] C. Haddock et al., arXiv:1802.05907, (2018), accepted for publication in Physics Letters (2018).
[2] F. M. Piegsa and G. Pignol, Phys. Rev. Lett. 108 (2012) 181801.
[3] C. Haddock et al., Nucl. Inst. Meth. A 885 (2018) 105–113

^{For the NSF Collaboration}