OPE, charm-quark mass, and decay constants of D and D_s mesons from QCD sum rules

TL;DR

This paper uses QCD sum rules to accurately determine the decay constants of D and D_s mesons, highlighting the importance of using MSbar masses over pole masses for better convergence and results.

Contribution

It demonstrates that reorganizing the perturbative expansion in terms of the MSbar mass improves convergence and yields more reliable decay constant estimates for charmed mesons.

Findings

Pole-mass expansion shows no convergence.

MSbar-mass expansion provides a clear hierarchy and better results.

Decay constants are more accurately determined using MSbar masses.

Abstract

We present a sum-rule extraction of the decay constants of the charmed mesons D and D_s from the two-point correlator of pseudoscalar currents. First, we compare the perturbative expansion for the correlator and the decay constant performed in terms of the pole and the running MSbar masses of the charm quark. The perturbative expansion in terms of the pole mass shows no signs of convergence whereas reorganizing this very expansion in terms of the MSbar mass leads to a distinct hierarchy of the perturbative expansion. Furthermore, the decay constants extracted from the pole-mass correlator turn out to be considerably smaller than those obtained by means of the MSbar-mass correlator. Second, making use of the OPE in terms of the MSbar mass, we determine the decay constants of both D and D_s mesons with an emphasis on the uncertainties in these quantities related both to the input QCD parameters and to the limited accuracy of the method of sum rules.