Next-to-Leading QCD and Finite Lifetime Effects in e+e- => t¿tH

One important task of the International Linear Collider (ILC) will be to determine the couplings of the Higgs boson. Since the top-quark is so heavy, the top Yukawa coupling is an especially interesting quantity. It is measured via top-pair associated Higgs production. Within the effective theory velocity Non-Relativistic QCD (vNRQCD) we calculated the next-to-leading logarithmic (NLL) QCD corrections as well as the NLL finite lifetime effects, which are relevant for the first phase of the ILC with a collision energy of 500GeV. The results show a strong enhancement of the total cross section relative to the naive Born computation and indicate a theoretical uncertainty of approximately 5% for the top Yukawa coupling measurement.