Chiral-invariant CP-violating effective interactions in Z decays to three jets

Tests of CP violation by appropriate momentum correlations in Z → 3 jets and in particular in Z → bbX probe CP-violating effective couplings — that manifest themselves as form factors — which conserve the quark chirality and quark flavour. By giving two examples we show that such couplings can be induced at one-loop order in extensions of the Standard Model with CP violation beyond the Kobayashi-Maskawa phase. In one of the models we compute the chirality-conserving part of the CP-violating Zbb-gluon amplitude for massless b quarks, determine the resulting effective dimension d = 6 couplings in the local limit, and discuss the possible size of the effects. Finally we show that in models with excited quarks the chiral-invariant CP-violating effective interactions could be quite large if appropriate couplings are of a size characteristic of a strong interaction.