Speaker: Eduardo DE RAFAEL
Title
Large-Nc QCD and Low Energy Interactions
Abstract
I shall first explain how, in the Standard Theory, the coupling constants
of the chiral Lagrangians of strong and electroweak interactions of
Goldstone particles at low energies, are related to
QCD Green's functions of color singlet operators. I shall then
show how these relations, when formulated within the framework of the
$1/N_c$--expansion, offer a systematic approach to calculate low energy
observables. I shall illustrate this with several examples: the
electroweak $\pi^{+}-\pi^{0}$ mass difference, the $\pi^{0}\rightarrow
e^{+}e^{-}$ and $\eta\rightarrow \mu^{+}\mu^{-}$ decay rates, the
$K\rightarrow \pi\pi$ amplitudes induced by ``penguin--type''
operators, $K^{0}-\bar{K}^{0}$ mixing, and the hadronic
$\gamma-\gamma-Z$ contributions to the muon $g-2$. Phenomenological
implications of the results obtained will also be discussed.