New CP-violation and preferred-frame tests with polarized electrons

We report new results from our torsion pendulum test for spin-coupled interactions. Our experiment uses the torque produced on a spin-polarized torsion pendulum containing 8$\times10^{22}$ polarized electrons as a sensitive measure of weak spin-coupled forces. Results can be interpreted as constraints on CP-violating interactions between the pendulum's polarized electrons and unpolarized matter in the surrounding environment, velocity-dependent interactions, and preferred-frame effects that would cause the electrons to precess about a direction fixed in inertial space. When interpreted in the context of Kosteleck\'y's Standard Model Extension, limits on CPT and Lorentz violating parameters are at the level of 10$^{-22}$~eV in the electron sector. These represent a factor of one hundred improvement over previously reported results, and should be compared to the benchmark value $m_e^2/M_{\rm P}= 2 \times 10^{-17}$~eV.