QCD scale in the heavy quark expansion.

Abstract

We argue that if one assumes a cutoff for the heavy quark chiral Lagrangian as high as the chiral-symmetry-breaking scale of about 1 GeV, then consistency of the combined heavy quark and chiral effective Lagrangian requires that the QCD scale which multiplies $\frac{1}{M}$ in the heavy quark expansion is also the chiral-symmetry-breaking scale. This means that either there is a large uncertainty in the accuracy with which the heavy quark effective theory can be applied to $c$ quarks, or the cutoff scale of the heavy quark chiral effective theory is lower than has been assumed.