The Quasi-Infra-Red Fixed Point at Higher Loops

Abstract

We calculate the four-loop $\beta$-function for the generalised Wess-Zumino model. We use the result and Padé-Borel summation to discuss the domain of attraction of the quasi-infra-red fixed point of the top-quark Yukawa coupling in the supersymmetric standard model, and argue that the domain is in fact substantial.

Comments: 12 pages, including 3 figures. Version as published in Phys. Lett. B, but with minor errors corrected, particularly f(T)-->f(0). Plain TeX. Uses Harvmac and epsf