Heavy and heavy to light quark expansions

Abstract

We analyze the phenomenon of heavy quark condensation within the framework of the QCD sum rule approach. We discuss two alternative expansions for massive quark condensates. The first one (heavy to light quark expansion), introduced by Broadhurst and Generalis, establishes a connection between the heavy and light quark worlds. The other one (heavy quark expansion) is valid when only heavy quark systems are considered. As a byproduct we have obtained the coefficients of$\left\langle {\bar qq} \right\rangle$,$\left\langle {\bar qGq} \right\rangle$, 〈G ²〉 and 〈G ³〉 for all bilinear currents.