Short-range tests of the equivalence principle

We tested the equivalence principle at short length scales by rotating a 3 ton ^238U attractor around a compact torsion balance containing Cu and Pb test bodies. The observed differential acceleration of the test bodies toward the attractor, a₂ₔ-a₏₁= (1. 02. 8) 10^-13 cm/s^2, should be compared to the corresponding gravitational acceleration of 9. 210^-5 cm/s^2. 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.