%0 Journal Article
%T A New Approach to Weak Amplitudes in Large-Nc QCD
%A M. Knecht
%A S. Peris
%A E. de Rafael
%A .
%J Physics
%D 1999
%I arXiv
%R 10.1016/S0920-5632(00)00577-6
%X We report on some recent progress made in understanding weak matrix elements of mesons in the context of the next-to-leading order of the large-Nc approximation to QCD. Specifically, we first use the example of the weak contributions to the pi^+ - pi^0 mass difference to exhibit how a systematic matching can be achieved analytically between short distances and long distances within our large-Nc framework. We are then also able to compute matrix elements of the operator Q_7, as they turn out to depend on the same QCD correlator as the previous pion mass difference. As a final example we determine the chiral counterterms governing the pseudoscalar decay into a lepton pair, where we briefly comment also on the special case K_L -> mu^+ mu^-.
%U http://arxiv.org/abs/hep-ph/9910396v1