An experiment to search for the production of neutral penetrating particles decaying into electron-positron pairs was performed with a 2.5-GeV electron beam. A total of 0.027 C was injected into a tungsten target. No such particle is found. Constraints on coupling constants ${\alpha }_e$ and ${\alpha }_{\gamma }$ are given.

• Received 5 May 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.659