New constraints on composition-dependent interactions weaker than gravity.

Abstract

Results from two recent ``fifth-force'' experiments disagree when analyzed in terms of a single baryonic interaction. We consider an interaction coupling to ${\mathrm{q}}_{5}$=B cos${\mathrm{\ensuremath{\theta}}}_{5}$+L sin${\mathrm{\ensuremath{\theta}}}_{5}$ where ${\mathrm{\ensuremath{\theta}}}_{5}$ has a value that could explain our null Cu-Be data while preserving Thieberger's positive Cu-${\mathrm{H}}_{2}$O result. (B and L are baryon and lepton number, respectively.) We present new Al-Be data that rule out this possibility except for a narrow region around ${\mathrm{\ensuremath{\theta}}}_{5}$\ensuremath{\approxeq}-63\ifmmode^\circ\else\textdegree\fi{} (${\mathrm{q}}_{5}$\ensuremath{\propto}${\mathrm{I}}_{3}$, the third component of isospin), where the ${\mathrm{q}}_{5}$ of terrestrial sources vanishes.