E+E- ANNIHILATION INTO HEAVY FERMION PAIRS AT HIGH-ENERGY COLLIDERS

We discuss the process e+e- --> ffBAR in the zero-width approximation for massive fermions which is complete at the electroweak 1-loop level. We present a detailed calculation of the electroweak loop diagrams in the massive fermion case. The formulae are applicable to the standard fermion production including a heavy top but also to heavy fermions of a possible next generation. Specific results are given for e+e- --> ttBAR in the standard model. Compared to the Born cross section the typical size of the weak corrections is about 10% if the top is light and has a wide range depending on the Higgs boson mass if the top is heavy. In particular close to threshold the influence of virtual Higgs bosons is quite significant for heavy top quarks with large Yukawa couplings culminating in weak corrections of the order of 40% if the Higgs is light. We also include QED corrections for the massive case complete in the virtual 1-loop part and in the soft-photon approximation for the real photon part.