SCHEME AND SCALE DEPENDENCES OF LEADING ELECTROWEAK CORRECTIONS

The scheme and scale dependences of leading M(t)-dependent contributio ns to Delta rho, Delta r, and tau, which arise because of the truncati on of the perturbative series, are investigated by comparing expressio ns in the on-shell and <(MS)over bar> schemes of renormalization, and studying their scale variations. Starting from the conventional on-she ll formulae, we find rather large scheme and scale dependences. We the n propose a simple, physically motivated modification of the conventio nal expressions and show that it leads to a sharp reduction in the sch eme and scale dependences. Implications for electroweak physics are di scussed.