Experimental bounds on interactions mediated by ultralow-mass bosons

We use a rotating torsion balance to search for feeble forces arising from exchange of ultralow-mass bosons. Our limits on the differential horizontal acceleration of Be/Al or Be/Cu test-body pairs in the field of the Earth, Δ$a_{\perp }$=(1.5±2.3)×${10}^{\mathrm{-}11}$ cm ${\mathrm{s}}^{\mathrm{-}2}$ and Δ$a_{\perp }$=(0.9±1.7)×${10}^{\mathrm{-}11}$ cm ${\mathrm{s}}^{\mathrm{-}2}$, respectively, set improved bounds on interactions mediated by bosons with masses ranging between ${10}^{\mathrm{-}17}$ and ${10}^{\mathrm{-}6}$ eV.