QCD CORRECTIONS TO LARGE-M(T) ELECTROWEAK EFFECTS IN DELTA-R - AN EFFECTIVE-FIELD THEORY POINT-OF-VIEW

By using effective field theory techniques for the standard model, we discuss the issue of what mu scale is the appropriate one in the QCD corrections to the large-m(t) electroweak contributions to hr. This needs the construction of an effective field theory below the top quark. We argue that, while matching corrections do verify the simple prescription of taking mu similar or equal to m(t) in alpha(s)(mu), logarithmic (i.e. similar to log m(t)) corrections do not, and require the use of the running alpha(s)(mu) in the corresponding renormalization group equation.