SINGLET QUARKS BEYOND THE TOP AT THE TEVATRON

The first evidence for the top quark at the Tevatron may indicate a cr oss section higher than the QCD expectation. We consider the possibili ty that isosinglet heavy quarks may be contributing to the signal and discuss ways of testing this possibility. For example, a charge 2/3 si nglet quark, approximately degenerate and mixing with the top quark, w ould effectively double the standard top signals. A similarly heavy ch arge -1/3 singlet quark mixing with the bottom quark would not affect top signals but would generate excess Z + multijet events with a b-tag .