What do heavy-light ($ Q\bar{q} $) quark systems tell us about QCD vacuum properties?

Abstract

Arguments in favor of a large magnitude ( at least two- three times bigger than its factorized value) of the mixed vacuum condensate $ \la \bar{q}G_{\mu\nu}^a G_{\mu\nu}^a q \ra$ are given. The analysis is based on the strict inequalities which follow from the QCD sum rules method and on very plausible phenomenological assumptions like $ m_{B_s} > m_{B_u} $ for the few lowest exited $ Q\bar{q} $ states in a heavy quark limit $m_Q\rightarrow\infty $. The same arguments show the suppression of the $SU(3)$ symmetry breaking effects for vacuum condensates when the additional gluon fields are included.