Search for new particles decaying into electron pairs of mass below 100 MeV/c2

We report results on 1220 electron pairs produced from a Pb-207 beam at 160 A GeV in nuclear emulsion with invariant mass Q ranging between 1 and 100 MeV and lifetime tau between 10(-15) s and 10(-12) s. These electron pairs were produced at a distance of more than 50 mu m from the primary interactions - this distance eliminates contamination due to Dalitz pairs. After subtracting the background pairs from the materialization of photons and also due to the decay of pi(0) -> 2 gamma from the data, they exhibit enhancement at low mass Q = 6-20 MeV with narrow peaks at 7 +/- 1 MeV, 19 +/- 1 MeV and tau <= 10(-13) s.