Couplings of heavy hadrons with soft pions from QCD sum rules

Abstract

We estimate the couplings in the Heavy Hadron Chiral Theory (HHCT) lagrangian from the QCD sum rules in an external axial field. Stability of the sum rules at moderate values of the Borel parameter is poor that probably signals a slow convergence of the OPE series. At large values of the Borel parameter they stabilize, and yield the couplings much lower than the constituent quark model expectations. This region is not trustworthy for baryons, but in the meson case only unexpectedly large contributions of a few lowest excitations could invalidate the prediction $g_1\approx0.2$.