We have searched for decays of the $\Upsilon \mathrm{}\left(1S\right)\mathrm{}$ into a single high-energy photon and a noninter-acting long-lived particle, using the CLEO detector at the Cornell Electron Storage Ring. An upper limit of 3 × ${10}^{-4\mathrm{}}$ (at 90% confidence level) is obtained for the branching ratio for such decays.

• Received 22 November 1982

DOI:https://doi.org/10.1103/PhysRevD.27.1665