New Test of the Gravitational $1\mathrm{/}{r}^2$ Law at Separations down to 52 $\mu$m

We tested the gravitational $1\mathrm{/}{r}^2$ law using a stationary torsion-balance detector and a rotating attractor containing test bodies with both 18-fold and 120-fold azimuthal symmetries that simultaneously tests the $1\mathrm{/}{r}^2$ law at two different length scales. We took data at detector-attractor separations between $52\mu$m and 3.0 mm. Newtonian gravity gave an excellent fit to our data, limiting with 95% confidence any gravitational-strength Yukawa interactions to ranges $<38.6\mu$m.