Width effects of the Z resonance and CP-violating asymmetry in e⁺e^- annihilation

Abstract

CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed out that such an absorptive part can be provided in e ⁺ e ^- annihilation by the presence of a Z(Z') resonance of non-zero width. The CP asymmetry in the process e⁺ e^- → l_il̅_j(l̅_il_j) , where l i are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry in e⁺ e^-→τ ⁺ e^- (τ^- e ⁺) is shown to be possible at LEP/SLC energies.