Collider implications of singlet fermions

We discuss some of the phenomenological implications when the standard electroweak model is extended to include singlet, vectorlike fermions with masses within the reach of TeV colliders. We show that for an arbitrary number of doublets and singlets, the flavor-violating Yukawa interactions involve only the fermion masses and the elements of the left-handed mixing matrix. Implications of this result for some recently proposed new physics possibilities at the hadronic colliders are discussed. These include model-independent restrictions for the exotic decay of the top quark t → cH, and also Z pair and Higgs-boson production from the decays of the singlet fermions