New limit on Lorentz and CPT-violating neutron spin interactions

Abstract

We performed a search for neutron spin coupling to a Lorentz and CPT-violating background field using a magnetometer with overlapping ensembles of K and ${}^3$He atoms. The co-magnetometer is mounted on a rotary platform for frequent reversal of its orientation. We measure sidereal oscillations in the signal to search for anomalous spin coupling of extra-solar origin. We determine the equatorial components of the background field interacting with the neutron spin to be ${\tilde{b}}_X^n=(0.1\pm 1.6)\times 10^{-33}$ GeV and ${\tilde{b}}_Y^n=(2.5\pm 1.6)\times 10^{-33}$ GeV, improving on the previous limit by a factor of 30. This measurement represents the highest energy resolution of any spin anisotropy experiment.