Revisiting f_B 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 f_B and the on-shell mass M_b 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 : \hat f_B^\infty=0.416(60) GeV^{3/2} in the static limit M_b \to \infty and the physical decay constant including 1/M_b corrections: f_B^{hqet}=199(29) MeV. Using the ratio of sum rules, we obtain, to order \alpha_s^2, 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 [1]: f_B^{qcd}=206(7) MeV and m_b(m_b)^{qcd}=4236(69) MeV. 
Stephan Narison (LUPM-CNRS Montpellier-FR)
hep-ph hep-ex hep-lat nucl-ex