Limits on new long range nuclear spin-dependent forces set with a K-3He co-magnetometer

TL;DR

This paper uses a K-3He co-magnetometer to set new experimental limits on long-range nuclear spin-dependent forces, constraining possible new physics beyond the Standard Model.

Contribution

It introduces a highly sensitive co-magnetometer technique to improve bounds on anomalous spin-dependent interactions at 50 cm scale.

Findings

Limits on neutron coupling to pseudoscalar and vector particles

Constraints on models involving unparticles and Lorentz symmetry breaking

Measurement of $^3$He spin precession frequency with 18 pHz resolution

Abstract

A magnetometer using spin-polarized K and $^3$He atoms occupying the same volume is used to search for anomalous nuclear spin-dependent forces generated by a separate $^3$He spin source. We measure changes in the $^3$He spin precession frequency with a resolution of 18 pHz and constrain anomalous spin forces between neutrons to be less than $2 \times 10^{-8}$ of their magnetic or less than $2\times 10^{-3}$ of their gravitational interactions on a length scale of 50 cm. We present new limits on neutron coupling to light pseudoscalar and vector particles, including torsion, and constraints on recently proposed models involving unparticles and spontaneous breaking of Lorentz symmetry.