RADIATIVE-CORRECTIONS FOR ASSOCIATED ZH PRODUCTION AT FUTURE E+E- COLLIDERS

The ZHffBAR four-point function is calculated in the one-loop approximation of the Standard Model and full analytic results are presented. The loop contributions due to both light and new heavy fermions are inspected in detail. The dominant mechanisms of Higgs-boson production from fermions are compared. The effect of radiative corrections on the cross section of ffBAR-->ZH including bremsstrahlung is studied. The spectrum of hard bremsstrahlung is integrated analytically. The implications for Higgs-boson searches at future e+e- colliders in the energy range 200 GeV less-than-or-equal-to square-root s less-than-or-equal-to 1.5 TeV, which includes both LEP 2 and the Next Linear Collider, are analyzed. For M(H)<2m(t) weak corrections in the modified on-mass-shell scheme are generally negative and feebly vary with M(H), while for M(H)>2m(t) they strongly increase with M(H) and may take large positive values. Electromagnetic corrections dramatically reduce the cross section close to the ZH-production threshold, while they may considerably enhance it far above this threshold.