Limits on possible new nucleon monopole-dipole interactions from the spin relaxation rate of polarized 3He gas

Various theories beyond the standard model predict new particles with masses in the sub-eV range with very weak couplings to ordinary matter. A P-odd and T-odd interaction between polarized and unpolarized nucleons proportional to (s) over right arrow . (r) over right arrow involving a scalar coupling g(s) at one vertex and a pseudoscalar coupling g(p) at the other vertex is one such possibility. We show that measurements of the transverse spin relaxation rate Gamma(2) for polarized gas can be used to set limits on g(s)g(p) for boson masses in the 10 mu eV to 100 meV range, corresponding to distances from centimeters to micrometers. We present limits from both a reanalysis of previous measurements of Gamma(2) in He-3 spin exchange cells and from data in a test experiment searching for a change in Gamma(2) upon the motion of an unpolarized test mass. The outlook for more sensitive measurements using this technique is discussed.