Various theories beyond the standard model predict new particles with masses in the sub-eV range with very weak couplings to ordinary matter. A new -odd and -odd interaction between polarized and unpolarized nucleons proportional to is one such possibility, where is the distance between the nucleons and is the spin of the polarized nucleon. Such an interaction involving a scalar coupling at one vertex and a pseudoscalar coupling at the polarized nucleon vertex can be induced by the exchange of spin-0 bosons. We used the NMR cell test station at Northrop Grumman Corporation to search for NMR frequency shifts in polarized and when a nonmagnetic zirconia rod is moved near the NMR cell. Long () spin-relaxation times allow precision measurements of the NMR frequency ratios, which are insensitive to magnetic field fluctuations. Combined with existing theoretical calculations of the neutron spin contribution to the nuclear angular momentum in xenon nuclei, the measurements improve the laboratory upper bound on the product by 2 orders of magnitude for distances near 1 mm. The sensitivity of this technique can be increased by at least two more orders of magnitude.
- Received 23 January 2013
© 2013 American Physical Society