RENORMALIZATION OF 4-QUARK OPERATORS AND QCD SUM-RULES

We compute the renormalization mismatch displayed in 1-loop approximation by classically equivalent 4-quark operators and coming from different possible definitions of the gamma5 matrix in dimensional regularization. The result is then employed to study the effect of the various treatments of gamma5 upon the size of radiative corrections to 4-quark condensates in the QCD sum rules for rho and A1 mesons. We find that a fully anticommuting gamma5 which automatically respects non-anomalous chiral Ward-Slavnov identities leads to considerably smaller corrections and reduces theoretical uncertainty in the QCD prediction for the tau hadronic decay rate.