Relative rates of W and Z events at the p¯p collider and nonstandard physics

We show that the data on the relative rates of W and Z events at the p¯p collider strongly disfavor a sequential charge -(1/3 quark b'with mb'<25 GeV. mb'is not restricted at all only if b'is a SU(2)L singlet, as is the case, e.g., in string-inspired E6 models. The same data indicate that the observation of weak gauginos in W/Z decays is unlikely