Short-range tests of the equivalence principle

TL;DR

This study conducts short-range tests of the equivalence principle using a rotating uranium attractor and a torsion balance, setting new limits on violations at centimeter scales and improving constraints over larger ranges.

Contribution

It provides the first short-range test of the equivalence principle with a rotating attractor and tightens bounds on possible violations at centimeter scales.

Findings

No violation detected within experimental uncertainty.

Set new constraints on Yukawa-range interactions down to 1 cm.

Improved limits on power law potentials from two-boson exchange.

Abstract

We tested the equivalence principle at short length scales by rotating a 3-ton $^{238}$U attractor around a compact torsion balance containing Cu and Pb test bodies. The observed differential acceleration of the test bodies toward the attractor, $a_{\text{Cu}}-a_{\text{Pb}} =(1.0\pm2.8)\times 10^{-13}$ cm/s$^2$, should be compared to the corresponding gravitational acceleration of $9.2\times10^{-5}$ 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.