Brown Abstract

Justin M. Brown
Princeton University

We performed a search for neutron spin coupling to a Lorentz - and CPT -violating background field using a magnetometer with overlapping spin ensembles of K and He3 atoms. The comagnetometer cancels external magnetic fields by a factor of 10^3-10^4, but remains sensitive to anomalous electron and neutron spin couplings. Our second generation apparatus uses a compact three-layer u-metal and inner ferrite shiled to further reduce magnetic interactions by a factor of 10^8. Furthermore, this comagnetometer is mounted on a rotating platform for frequent reverals of its orientation. We measure sidereal oscillations in the signal to search for anomalous spin coupling of an extra-solar origin. Since the comagnetometer is also a sensitive gyroscope, Earth's rotation contributes significantly to the signal. In my talk, I will describe the K-He3 comagnetometer and the effects of rotating the apparatus, especially the systematic effects caused by Earth's rotation as a background field. I present the most sensitive spin anisotropy limit, b<3.7 X 10^-33 GeV, improving upon the previous limit for the neutron by a factor of 30. Finally, I will discuss the some current development of our third generation experiment using the new K-Rb-Ne21 comagnetometer. It has already demonstrated improved sensitivity to anomalous fields and we propose continuing tests of a variety of spin-dependent interactions.