Experimental constraints on exotic spin-dependent interactions using specialized materials

Various theories predict the possible existence of symmetry violating forces with mesoscopic range interactions from mm-m [1]. These forces can arise from the coupling of a spin 0 boson to spin 1/2 fermions through scalar (gs) and pseudoscalar (gp) couplings. We discuss two experiments that can investigate these interactions using nucleon rich, impressively low magnetic susceptibility (5-100 times lower than pure water) test masses and electron-spin rich, polarized test masses (spin density: 10 20 h/cm3 ). The first experiment looks for a P-odd, T-odd interaction potential proportional to (S.r) where S is the spin of one particle and r is the unit vector pointing from the first particle to the second. We use ensembles of polarized nuclei and the unpolarized low magnetic susceptibility masses along with NMR techniques to search for such a potential over sub-mm ranges. We established an improved upper bound on the product gsgnp of the scalar coupling to particles in the unpolarized mass and the pseudoscalar coupling of polarized neutrons for force ranges from 10 -4 to 10 -2 m, corresponding to a mass range of 2*10 -3 to 2*10 -5 eV for the exchange boson [2]. The second experiment proposes to investigate several electron-spin dependent potentials. It will use polarized electron masses as the source of pseudo scalar vertex and double planar 1kHz mechanical oscillators to look for such potentials over the sub-mm range. The projected sensitivity for this experiment surpasses the existing experimental limits for several of the spin dependent interactions by 4-8 orders of magnitude for ranges below 10 -3m [3]