Improved f_{D*_(s)}, f_{B*_(s)} and f_{B_c} from QCD Laplace sum rules

TL;DR

This paper improves estimates of decay constants for D*, B*, and B_c mesons using advanced QCD sum rules, aiming to aid future CKM angle measurements with reduced systematic uncertainties.

Contribution

It introduces refined calculations of meson decay constants using inverse Laplace sum rules with higher-order QCD corrections and stability criteria, enhancing previous estimates.

Findings

More precise decay constant values for D*, B*, and B_c mesons.

Inclusion of N2LO perturbative and d=6 non-perturbative contributions.

Results compared favorably with recent estimates.

Abstract

Anticipating future precise measurements of the D- and B-like (semi-)leptonic and hadronic decays for alternative determinations of the CKM mixing angles, we pursue our program on the D- and B-like mesons by improving the estimates of f_{D*_(s)} and f_{B*_(s)} (analogue to f_\pi) by using the well-established (inverse) Laplace sum rules (LSR) and / or their suitable ratios less affected by the systematics, which are known to N2LO pQCD and where the complete d = 6 non-perturbative condensate contributions are included. The convergence of the PT series is analyzed by an estimate of the N3LO terms based on geometric growth of the coefficients. In addition to the standard LSR variable {\tau} and the QCD continuum threshold t_c stability criteria, we extract our optimal results by also requiring stability on the variation of the arbitrary QCD subtraction point {\mu}. We complete the analysis by a direct estimate of f_{B_c}. Our results summarized in Tables III and IV are compared with some other recent estimates.