search for single photons from radiative neutrino or supersymmetric-particle production

A search for single photons produced in association with neutrinos or other weakly interacting neutral particles has been performed in e^+e^- annihilations at s=29 GeV with the MAC detector at the SLAC e^+e^- storage ring PEP. One event is observed, with 1. 1 events expected from the reaction e^+e^-. The number of neutrino families is restricted to N_48 GeV/c^2 at the 90% confidence level if m { \~{e}₋}=m { \~{e}ₑ} and m \~{}=0. If m { \~{e}₋}>>m { \~{e}ₑ}, the corresponding limit is m { \~{e}ₑ}>40 GeV/c^2.