Heavy-meson decay constants from QCD sum rules

TL;DR

This paper uses QCD sum rules with a new dual threshold method to accurately determine decay constants of heavy mesons D, D_s, B, and B_s, controlling uncertainties from QCD parameters and method limitations.

Contribution

It introduces a novel procedure for extracting hadron observables with improved uncertainty control, especially regarding the dual threshold depending on the Borel parameter.

Findings

Calculated decay constants for D and D_s mesons with uncertainties.

Determined the b-quark MSbar mass by matching sum-rule results to lattice data.

Estimated decay constants for B and B_s mesons with quantified uncertainties.

Abstract

We sketch a recent sum-rule extraction of the decay constants of the heavy pseudoscalar mesons D, D_s, B, and B_s from the two-point correlator of heavy-light pseudoscalar currents [1]. Our main emphasis lies on the control over all the uncertainties in the decay constants, related both to the input QCD parameters and to the limited accuracy of the method of sum rules. Gaining this control has become possible by application of our new procedure of extracting hadron observables based on a dual threshold depending on the Borel parameter. For the charmed-meson decay constants, we find f_D=206.2\pm 7.3(OPE) \pm 5.1(syst) MeV, f_Ds=245.3\pm 15.7(OPE) \pm 4.5(syst) MeV. For the beauty mesons, the decay constants turn out to be extremely sensitive to the precise value of the MSbar mass of the b-quark, mb(mb). By requiring our sum-rule estimate to match the average of the lattice determinations of f_B, we extract the rather accurate value mb(mb)=(4.245\pm 0.025) GeV. Feeding this parameter value into our sum-rule formalism leads to the beauty-meson decay constants f_B = 193.4 \pm 12.3(OPE) \pm 4.3(syst) MeV, f_Bs =232.5 \pm 18.6(OPE) \pm 2.4(syst) MeV.