Search for anomalous single-photon production at thee+e−storage ring PEP

This Letter reports a search for the production by $e^{+}$ $e^{\mathrm{-}}$ annihilation of a single photon accompanied by particles that interact only weakly in matter. The search was performed at the SLAC $e^{+}$ $e^{\mathrm{-}}$ storage ring PEP (√s =29 GeV) with a new detector, ASP. No unexpected signal was observed. The limit $N_{\nu }$51 GeV/$c^2$ (90% C.L.) for $m_{\gamma ̃}$=0 and degenerate ẽ mass states.