New Constraints on Short-Range Forces Coupling Mass to Intrinsic Spin

A new device that we refer to as the spherical superconducting torsion balance has been used to search for a new force coupling mass to intrinsic spin. Our experimental approach also employs a novel spin-source geometry that allows unprecedented sensitivity in the range 100 μm<λ<5 mm. We place new limits on the dimensionless coupling constant of such an interaction of ${g}ₚᵉ{g}ₛ<({-}1.9±{}(1.3{)}ₛₜₐₜ±{}(1.5{)}syst)×{}{10}^{{-}26}$ for ${λ}>10 mm$ at $1{σ}$ confidence. At a range of 1 mm our most relaxed limit is ${g}ₚᵉ{g}ₛ<1.5×{}{10}^{{-}24}$.