Search for $Q=\frac{2}{3}e$ and $Q=\frac{1}{3}e$ Particles Produced in $e^{+}{e}^{-}$ Annihilations

In a search for heavy $Q=\frac{2}{3}e$ and $Q=\frac{1}{3}e$ particles produced in $e^{+}{e}^{-}$ collisions at a center-of-mass energy of 29 GeV, no candidate events were found in 77 ${\mathrm{pb}}^{-1\mathrm{}}$ of data collected by the time projection chamber at PEP. Upper limits are established on the inclusive cross section for the production of $Q=\frac{2}{3}e$ and $Q=\frac{1}{3}$ particles in the mass range 1-13 GeV/${\mathit{c}}^2$, improving upon previously established limits.