Revisiting fB and m¯b(m¯b) from HQET spectral sum rules

Using recent values of the QCD (non-) perturbative parameters given in Table 1, we reconsider the extraction of fB and the on-shell mass Mb from HQET Laplace spectral sum rules known to N2LO PT series and including dimension 7 condensates in the OPE. We especially study the convergence of the PT series, the effects on “different spectral sum rules data” of the continuum threshold and subtraction point varied in a larger range than in the existing literature and include in the error an estimate of the N3LO PT series based on a geometric growth of the PT series. We obtain the Renormalization Group Invariant (RGI) universal coupling: fˆB∞=0.416(60)GeV3/2 in the static limit Mb→∞ and the physical decay constant including 1/Mb corrections: fBhqet=199(29)MeV. Using the ratio of sum rules, we obtain, to order αs2, the running mass m¯b(m¯b)=4213(59)MeV. The previous results are in good agreement with the ones from QCD spectral sum rules (QSSR) in full QCD to the same order from the same channel Narison (2013) [1]: fBqcd=206(7)MeV and m¯b(m¯b)qcd=4236(69)MeV.