Initial State Radiation to Off-shell Z⁰ Pair Production in e^+e^- Annihilation

A study of the Standard Model reaction $\e^+e^- \rightarrow (\Z^0\Z^0) \rightarrow f_1\bar{f_1}f_2\bar{f_2}$ including the effects of the finite $\Z^0$~width and initial state radiative corrections is presented. All angular phase space integrations are performed analytically. The remaining invariant masses are integrated numerically. Semi-analytical and numerical results in the energy range $\RS=200\;GeV$ to $1\;TeV$ are reported.