Top quark couplings at ILC : six and eight fermion final states ∗

I discuss the calculation of cross sections for processes with six and eight fermions in the final state, contributing to single-top production and associated top-Higgs production at a linear collider. I describe the schemes for the treatment of finite decay widths implemented in the matrix element generator O’Mega and give a numerical comparison for single-top production. In the case of single top production, after reducing vector boson fusion backgrounds by appropriate cuts, the effect of including the full six fermion final state amounts to 2−5%. In associated top-Higgs production, non-resonant electroweak backgrounds are of a similar magnitude while QCD backgrounds are much larger. Extended notes for a talk given at the 2nd Workshop of the ECFA Study ‘Physics and Detectors for a Linear Collider’ , 1.-4.9 2004, Durham [email protected]