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 $\sqrt{s}=29\mathrm{}$ 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 $e^{+}{e}^{-}\to \nu \overline{\nu }\gamma$. The number of neutrino families is restricted to $N_{\nu }<17\mathrm{}$ at the 90% confidence level. Limits on possible masses of supersymmetric electrons ($\tilde{e}$) and photons ($\tilde{\gamma }$) are presented. The $\tilde{e}$ mass limit is $m_{\tilde{e}}>48\mathrm{}$ GeV/${\mathit{c}}^2$ at the 90% confidence level if $m_{{\tilde{e}}_L}=m_{{\tilde{e}}_R}$ and $m_{\tilde{\gamma }}=0\mathrm{}$. If $m_{{\tilde{e}}_L}>>m_{{\tilde{e}}_R}$, the corresponding limit is $m_{{\tilde{e}}_R}>40\mathrm{}$ GeV/${\mathit{c}}^2$.