This paper reports the results of a study of hadron production in $e^{+}{e}^{-}$ collisions at c.m. system energies of 33, 35, and 35.8 GeV. Production of a new quark flavor has been sought. The measured values of the total cross section, the thrust distributions, and the study of inclusive muon production show no evidence for the production of a new charge-$\frac{2}{3}e$ quark near threshold. In addition, during an energy scan in the region $29.9<~\sqrt{s}<~31.6$ GeV, no hadron resonance indicating the existence of a bound state composed of charge-$\frac{2}{3}e$ quarks has been found.

• Received 1 April 1980

DOI:https://doi.org/10.1103/PhysRevLett.44.1722