Threshold Effects on the QCD Coupling ${\alpha }_{\overline{MS}}$

Abstract

The matching condition which determines the effect of a heavy quark threshold on the running of the QCD coupling ${\alpha }_{\overline{MS}}$ is reviewed. The matching scale is arbitrary to some extent. However, this affects the value of ${\alpha }_{\overline{MS}}$ away from the threshold region only marginally.

7 pages, PITHA 94/31