HIGGS RADIATION OFF TOP QUARKS IN ee COLLISIONS

The strength of the Yukawa coupling of the leptons and quarks with the Higgs boson is uniquely determined by the Higgs mechanism for generating masses in the Standard Model. The top-Higgs coupling can be measured directly in the process ee → tt̄H. This process therefore provides a fundamental test of the Higgs mechanism. Extending earlier analyses carried out in the Born approximation, we have determined the cross section for this process including QCD corrections, which turn out to be important. Permanent address Supported by Bundesministerium für Bildung und Forschung (BMBF), Bonn, Germany, under Contract 05 7 HH 92P (5), and by EU Program Human Capital and Mobility through Network Physics at High Energy Colliders under Contract CHRX-CT93-0357 (DG12 COMA). 1. The masses of the fundamental particles are generated in the Higgs mechanism [1] by interactions with the non-zero Higgs field in the ground state. Within the Standard Model, the Yukawa couplings of the leptons and quarks with the Higgs particle are therefore uniquely determined by the particle masses: