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

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(α 2 s ) terms in the perturbative part and calculating the O(α s ) corrections to the quark-condensate contribution. With this accuracy, we obtain the ratios of decay constants: f B * /f B = 1.02 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.

Form factors of B, Bs → η (′) and D, Ds → η (′) transitions from QCD light-cone sum rules

“…We have used the same level of accuracy as in the calculation of the form factors, i.e O(α s ) in both, the perturbative and nonperturbative (quark condensate) part and in the determination of the sum rules parameters s .5), (3.6), (3.7). By comparing our results with the previous LCSR results and the most recent determinations from [34], where in the perturbative part the higher order corrections were included, we see a good agreement. The results are also within uncertainties of the lattice QCD calculations of the same decay constants [35][36][37].…”

B s → Kℓν ℓ and B (s) → π(K)ℓ + ℓ − decays at large recoil and CKM matrix elements

“…The effective quark-hadron duality threshold is determined calculating the B (s) -meson mass from the differentiated LCSR. The decay constants f B and f Bs entering LCRSs are replaced by the two-point sum rules in NLO, their expressions and input parameters (in particular, the vacuum condensate densities) are the same as in [8]. The intervals obtained from these sum rules in NLO are f B = (202 +35 −21 ) MeV, f Bs = (222 +38 −24 ) MeV.…”

“…For the quark masses in M S scheme, entering the correlation functions for QCD sum rules, we adopt, following, e.g., [8], the intervals covering the non-lattice determinations in [17]. We put…”

“…In particular, we correct certain terms in the subleading twist-3,4 contributions to LCSRs for both vector and tensor form factors. In parallel, we recalculate the B → K and B → π form factors using a common set of input parameters, e.g., the updated [8] 2-point QCD sum rule for the decay constants f B and f Bs . Importantly, the twist-5,6 corrections to the LCSRs estimated by one of us [9] are negligibly small, ensuring the reliability of the adopted twist ≤ 4 approximation.…”

B meson decay constants f B c $$ {f}_{B_c} $$ , f B s $$ {f}_{B_s} $$ and f B from QCD sum rules

“…QCDSR calculations have narrowed the range of results to f B = 189 − 207 MeV, and f Bs = 216 − 242 MeV [16,17]- [19], while LQCD calculations, claiming high accuracy, give f B = 186 − 205 MeV, and f Bs = 224 − 244 MeV [20][21][22][23][24][25]. For B c a compilation of many LQCD determinations [26] gives values in the wide range f Bc = 380 − 680 MeV.…”