New Test of the Equivalence Principle from Lunar Laser Ranging

An analysis of six years of lunar-laser-ranging data gives a zero amplitude for the Nordtvedt term in the Earth-Moon distance yielding the Nordtvedt parameter $\eta =0.00\mathrm{}\pm 0.03$ Thus, Earth's gravitational self-energy contributes equally, ±3%, to its inertial mass and passive gravitational mass. At the 70% confidence level this result is only consistent with the Brans-Dicke theory for $\omega >29\mathrm{}$. We obtain $|\beta -1|\lesssim 0.02 \mathrm{to} 0.05$ for five-parameter parametrized post-Newtonian theories of gravitation with energy-momentum conservation, or $|\beta -1|\lesssim 0.01$ if only $\beta$ and $\gamma$ are considered.