Improved constraints on non-Newtonian forces at 10 microns

Several recent theories suggest that light moduli or particles in large extra dimensions could mediate macroscopic forces exceeding gravitational strength at length scales below a millimeter. Such new forces can be parameterized as a Yukawa-type correction to the Newtonian potential of strength alpha relative to gravity and range lambda. To extend the search for such new physics we have improved our apparatus utilizing cryogenic micro-cantilevers capable of measuring attonewton forces, which now includes a switchable magnetic force for calibration. Our most recent experimental constraints on Yukawa-type deviations from Newtonian gravity are more than 3 times as stringent as our previously published results and represent the best bound in the range of 5-15 mu m, with a 95% confidence exclusion of forces with |alpha|> 14,000 at lambda=10 mu m.