Momentum subtraction and the R-ratio

Abstract

We determine the R-ratio for massless quarks in several renormalization schemes to various loop orders. These are the momentum subtraction schemes of Celmaster and Gonsalves as well as the minimal momentum subtraction scheme. The dependence of the R-ratio on the schemes is analysed.

Comments: 27 latex pages, 36 figures, anc directory contains txt file with electronic version of main equations