Decay constants of heavy mesons from QCD sum rules

TL;DR

This paper uses QCD sum rules with a novel dual threshold method to accurately determine decay constants of heavy mesons like D, Ds, B, and Bs, controlling uncertainties from QCD parameters and methodological limitations.

Contribution

The paper introduces a new procedure for extracting hadron observables with a Borel-dependent dual threshold, improving uncertainty control in decay constant calculations.

Findings

Accurate decay constants for D and Ds mesons: f_D=206.2±7.3±5.1 MeV, f_Ds=245.3±15.7±4.5 MeV.

Precise determination of b-quark MSbar mass: mb(mb)=4.245±0.025 GeV.

Decay constants for B and Bs mesons consistent with lattice results: f_B=193.4±12.3±4.3 MeV, f_Bs=232.5±18.6±2.4 MeV.

Abstract

We present a sum-rule extraction of the decay constants of the D, Ds, B, and Bs mesons from the two-point correlator of heavy-light pseudoscalar currents [1]. Our main emphasis is laid on the control over 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 due to the application of our novel procedure for extracting hadron observables based on a dual threshold depending on the Borel parameter. For charmed mesons, we obtain f_D=206.2\pm 7.3 (OPE)\pm 5.1 (syst) MeV and f_Ds=245.3\pm 15.7 (OPE) \pm 4.5 (syst) MeV. For 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 lattice determinations of f_B, a very accurate value is extracted, mb(mb)=4.245\pm 0.025 GeV, yielding f_B = 193.4 \pm 12.3 (OPE) \pm 4.3 (syst) MeV and f_Bs = 232.5 \pm 18.6 (OPE) \pm 2.4 (syst) MeV.