Searching for a dark photon: project of the experiment at VEPP-3

We propose an experiment to search for a new gauge boson A' in e(+)e(-) annihilation by means of a positron beam incident on a gas hydrogen target internal to the bypass at the VEPP-3 storage ring. The search method is based on a missing mass spectrum in the reaction e(+) e(-) -> gamma A'. It allows observation of the A' signal independently of its decay modes and life time. The projected result of this experiment corresponds to an upper limit on the square of the coupling constant epsilon(2) = 3.10(-8) with a signal-to-noise ratio of two to one at an A' mass of 5-20 MeV.