Effects of mixing between ordinary and exotic charged leptons in the process e+e--->Z0Z0.

Abstract

The process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{Z}^{0}{Z}^{0}$ is reexamined with the inclusion of mixing between ordinary and exotic charged leptons. Three types of exotic leptons, (i) mirror, (ii) vector doublet, and (iii) vector singlet, are considered. The effects of mixing are discussed in terms of the expected relative deviations in the differential decay parameters with respect to the standard-model results. These are presented as a function of the scattering angle as well as a function of the square of mixing, ${|{U}_{\mathrm{Ee}}|}^{2}$, between the ordinary ($e$) and exotic ($E$) leptons. At $\sqrt{s}=200$ GeV, ${m}_{E}=100$ GeV, and ${|{U}_{\mathrm{Ee}}|}^{2}=0.02$, for the mixing of the three types of leptons, the expected relative deviations are (i) between -2.7% and -7.6% in the differential cross sections with unpolarized ${e}^{+}$, ${e}^{\ensuremath{-}}$ beams, (ii) between \ensuremath{\sim} -6% and \ensuremath{\sim} -8% in the inclusive angular distributions (for the production of polarized ${Z}^{0}'\mathrm{s}$) with longitudinally polarized ${e}^{\ensuremath{-}}$ and unpolarized ${e}^{+}$ beams, and (iii) between +10.4% and -11% in the differential polarization asymmetry. The magnitudes of the relative deviations, in most of these decay parameters, increase with the increase in ${m}_{E}$. We find that, in principle, measurements of relative deviations in the polarization asymmetry and inclusive angular distributions with ${e}_{L(R)}^{\ensuremath{-}}$,${e}^{+}$ beams could help in distinguishing mirror, vector-doublet, and vector-singlet lepton mixings.