Large pion pole in Z(S)(MOM)/Z(P)(MOM) from Wilson action data

We show that, contrarily to recent claims, data from the Wilson (unimproved ) fermionic action at three different beta values demonstrate the presence of a large Goldstone boson contribution in the quark pseudoscalar vertex, q uantitatively close to our previous estimate based on the SW action with c( SW) = 1.769. We show that discretisation errors on Z(S)(MOM)/Z(P)(MOM) seem to be much smaller than the Goldstone pole contribution over a very large range of momenta. The subtraction of this non perturbative contribution lea ds to numbers close to one-loop BPT. (C) 2001 Published by Elsevier Science B.V.