Operator Product Expansion, Renormalization Group and Weak Decays

Abstract

A non-technical description of the Operator Product Expansion and Renormalization Group techniques as applied to weak decays of mesons is presented. We use this opportunity to summarize briefly the present status of the next-to-leading QCD corrections to weak decays and their implications for the unitarity triangle, the ratio epsilon prime/epsilon, the radiative decay B-> s gamma, and the rare decays K^+ -> pi^+ nu barnu and K_L to pi^0 nu barnu.