G.J. Gounaris1 - P.I. Porfyriadis1 - F.M. Renard2
1 Department of Theoretical Physics, University of Thessaloniki,
GR-54006, Thessaloniki, Greece
2 Physique Mathématique et Théorique, UMR 5825 Université Montpellier II, F-34095 Montpellier Cedex 5, France
Received: 3 February 1999 / Pulished online: 30 June 1999
We study the helicity amplitudes of the process at high energy, which in the standard and SUSY models first arise at the one-loop order. In the standard model (SM), the diagrams involve W, charged-quark, and lepton loops, while in SUSY, we also have contributions from chargino-, charged-sfermion, and Higgs-loop diagrams. The SUSY contributions are most important in the region above the threshold for producing the supersymmetric partners; there, they interfere most effectively with the primarily imaginary SM amplitudes. Simple expressions for the relevant one-loop functions are given which provide a direct overview of the behaviour of the helicity amplitudes in the whole parameter space at high energies. The various characteristics of a large set of observables are studied in detail.