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 α relative to gravity and range λ. 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 μm, with a 95% confidence exclusion of forces with |α|>14,000 at λ=10 μm.