Hard-soft renormalization of the massless Wess-Zumino model

We show that in a Wilsonian renormalization scheme with zero-momentum subtraction point the massless Wess-Zumino model satisfies the non-renormalization theorem; the finite renormalization of the superpotential appearing in the usual non-zero momentum subtraction schemes is thus avoided. We give an exact expression of the beta and gamma functions in terms of the Wilsonian effective action; we prove the expected relation $\beta = 3g\gamma$. We compute the beta function at the first two loops, finding agreement with previous results.