Spin Mass Interaction Limiting Experiment (SMILE)

We present preliminary results of an upcoming experiment to limit possible anomalous spin mass interactions. Such interactions arise naturally if light pseudoscalar bosons like the axion exist and a bound on such interactions places constraints on the couplings of the axion, which is of particular interest both as a solution to the strong CP problem in QCD and as a dark matter candidate. In this experiment, we measure the couplings of the axion using a $^3$He-K co-magnetometer by modulating the positions of two 200kg source masses that produces an energy shift in the atoms proportional to the axion's coupling constants. Astroyphysical observations\footnote{G. Raffelt, Phys. Rev. D \textbf{86}, 015001 (2012).} currently exceed the best laboratory limits\footnote{A. N. Youdin, D. Krause, Jr., K. Jagannathan, and L. R. Hunter, Phys. Rev. Lett. \textbf{77}, 11 (1996).} of light axions' couplings to nucleons by two order of magnitudes but we expect, for the first time in a laboratory experiment, to surpass those astrophysical bounds. Construction of the experiment has been completed and we present here some preliminary results and discuss possible systematic effects. Supported by NSF PHY-1404325.