Decay constants of heavy-light vector mesons from QCD sum rules

TL;DR

This paper refines QCD sum rule calculations for heavy-light meson decay constants by including higher-order corrections, leading to more accurate and updated predictions for both vector and pseudoscalar mesons, and examines heavy-quark symmetry violations.

Contribution

It introduces higher-order perturbative and condensate corrections into QCD sum rules for meson decay constants, improving accuracy and exploring heavy-quark symmetry violations.

Findings

Ratios of vector to pseudoscalar decay constants close to unity.

Updated decay constant values with quantified uncertainties.

Analysis of sum rule sensitivity and heavy-quark symmetry violations.

Abstract

We revisit QCD sum rules for the decay constants of heavy-light mesons. In the sum rules for the vector mesons B^*_(s) and D^*_(s) we improve the accuracy of OPE, taking into account the O(alpha_s^2) terms in the perturbative part and calculating the O(alpha_s) corrections to the quark-condensate contribution. With this accuracy, we obtain the ratios of decay constants: f_B^*/f_B=1.02 +0.07 -0.03, f_D^*/f_D=1.20 +0.10 -0.07. The sum rule predictions for the decay constants of pseudoscalar mesons are updated with the results f_B=(207 +17 -9) MeV, f_B_s=(242 +17 -12) MeV, f_D=(201 +12 -13) MeV, f_D_s=(238 +13 -23) MeV. In order to assess the sensitivity of our calculation to the form of the sum rule, we consider alternative versions such as the power moments and Borel sum rules with different weights of the spectral density. We also investigated the heavy quark limit of the sum rules for vector and pseudoscalar mesons, estimating the violations of the heavy-quark spin and flavour symmetry.