Upper limits for the production of light short-lived neutral particles in radiative Upsilon decay.

We have searched for the exclusive decay of the UPSILON(1S-italic) into a photon and a short-lived spin-0 particle, a-italic, decaying into e-italic/sup +/e/sup -/, using the CLEO detector at the Cornell electron storage ring. Upper limits for the product branching ratio B-italic(UPSILON(1S-italic)..--> gamma..a-italic) x B-italic(a-italic..-->..e-italic/sup +/e/sup -/) are established for a range of masses, 2m-italic/sub e-italic/