Short-range tests of the equivalence principle

We tested the equivalence principle at short length scales by rotating a 3 ton U-238 attractor around a compact torsion balance containing Cu and Pb test bodies. The observed differential acceleration of the test bodies toward the attractor, a(Cu)-a(Pb)=(1.0 +/- 2.8) x 10(-13) cm/s(2) should be compared to the corresponding gravitational acceleration of 9.2x10(-5) cm/s2 Our results set new constraints on equivalence-principle violating interactions with Yukawa ranges down to 1 cm, and improve by substantial factors existing limits for ranges between 10 km and 1000 km. Our data also set strong constraints on certain power-law potentials that can arise from two-boson exchange processes.