OPE, Heavy-Quark Mass, and Heavy-Meson Decay Constants from QCD Sum Rules

Understand

We present a sum-rule extraction of the decay constants of heavy-light mesons from the two-point correlator of pseudoscalar currents.

• To this end, we compare the perturbative expansions for the correlator and the decay constant performed in terms of either the pole mass or the running MS-bar mass of the heavy quark.
• The perturbative expansion expressed in terms of the pole mass exhibits no sign of convergence whereas reorganizing this very expansion in terms of the MS-bar mass yields a rather clear hierarchy of the perturbative contributions.
• Accordingly, the decay constants extracted from the pole-mass correlator turn out to be considerably smaller than those extracted from its MS-bar-mass counterpart.