Minimal subtraction and the decoupling of heavy quarks for arbitrary values of the gauge parameter

Abstract

The decoupling of a heavy quark is investigated to two loops for QCD renormalized by minimal subtraction. It is shown that the heavy quark effects can be absorbed into an effective coupling constant, an effective gauge parameter and effective masses for the light quarks. The relations between these effective parameters and the parameters of the full theory are gauge invariant. In terms of the effective parameters the theory satisfies renormalization group equations which refer only to the light degrees of freedom.