Flavor changing Z0 decay and the top quark

The flavor changing neutral current decay of the Z0 boson into charge 2/3 quarks in the standard three generation SU(2)sub(L) x U(1) theory of electroweak interactions has been studied. This process occurs first at one-loop order, where it has been calculated without approximation. The possibility of producing the as yet undiscovered top quark by this decay has been considered. The branching ratios are extremely small, independent of the top quark mass and plausible quark mixing matrices if there are three generations, making it unlikely that the top quark will be produced by this mechanism. However, a massive fourth bottom quark could increase the rates. (orig.)