QCD Decoupling at Four Loops s

We present the matching condition for the strong coupling con-tant α (n f) s at a heavy quark threshold to four loops in the modified minimal subtraction scheme. Our results lead to further decrease of the theoretical uncertainty of the evolution of the strong coupling constant through heavy quark thresholds. Using a low energy theorem we furthermore derive the effective coupling of the Higgs boson to gluons (induced by a virtual heavy quark) in four-and (partially) through five-loop approximation.