Test of the equivalence principle for ordinary matter falling toward dark matter

We tested the equivalence principle (EP) for Be, Cu, and Al falling toward the galactic center, and found Δa(Be,Cu)=-(0.1 ±5.8)×${10}^{\mathrm{-}12}$ cm/${\mathit{s}}^2$ and Δa(Be,Al)=(3.6±6.9)×${10}^{\mathrm{-}12}$ cm/${\mathit{s}}^2$. As dark matter is thought to account for (25–30)% of our galacticentric acceleration, the EP parameters for Be/Cu, or Be/Al, falling toward dark matter, are η(Be,Cu)=(0.0±1.2)×${10}^{\mathrm{-}3}$ and η(Be,Al)=(0.7±1.4)×${10}^{\mathrm{-}3}$ (1σ errors). This limits any EP-violating component of our acceleration toward dark matter and provides laboratory evidence that gravitation is the only significant long-range interaction between dark and ordinary matter.