Search for Fractionally Charged Particles

A search was made for fractionally charged particles produced by 12 GeV electrons incident on a copper target. No such particles were detected. Comparison with calculations on photoproduction of pairs of these particles enable lower limits to be placed on the masses of such particles which may exist. Particles of the type discussed in this paper (pure spin one half Dirac particles with no strong interactions) do not exist with masses below these limits. These limits are dependent on the charge and lifetime assigned to the particle. For lifetimes 5: 10 -7 set, the lower limit varies from 0.2 GeV for 0.04 e charge, to 1.5 GeV for 0.7 e charge. For lifetimes 2 10 -ILo set and 0.7 e charge the lower limit is 1.2 GeV.