QCD-duality approach to non-leptonic weak transitions : towards an understanding of the |DELTA.I| = 1/2 rule

Abstract

The progress done in the QCD-duality analysis of strangeness changing nonleptonic weak transitions is reviewed. The method combines the information provided by the effective chiral realization of QCD at long distances with its perturbative short-distance behaviour, via a duality approach. Special attention is given to the failure of the earlier leading-logarithm calculations in explaining the observed |AI| = 1/2 K -- pipi amplitude. It is shown that the next-to-leading alfas corrections to the |AI| = 1/2 correlator are enormous, and with the appropriate sign to produce the required enhancement.