E- ANNIHILATION INTO HEAVY-FERMION PAIRS IN THE 2 HIGGS-DOUBLET MODEL(E)

Electroweak radiative one-loop corrections to heavy-fermion pair produ ction in e+e- annihilation are calculated in the two Higgs-doublet ext ension of the standard model. The numerical size of the additional non -standard corrections is discussed for the process e+e- --> ttBAR. The relative difference between the predictions of the two Higgs-doublet model and the minimal standard model is typically of the order of a fe w percent. For a light scalar Higgs, however. the difference can be of the order of 10% at high energies and even larger close to threshold. If one imposes the supersymmetric constraints on the parameters of th e Higgs sector, the difference is usually below approximately 2%; for a light pseudoscalar and close to threshold it reaches 4%.