1212.5544 (Stephan Narison)

Revisiting f_B and m_b(m_b) from HQET spectral sum rules    [PDF]

Stephan Narison

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 : f_B^infinity=0.407(28) GeV^3/2 in the static limit M_b to infinity and the physical decay constant including 1/M_b corrections: f_B^hqet=197(13) MeV. Using the ratio of sum rules, we obtain the on-shell b quark mass M_b=4871(30) MeV to order alpha_s^2 from which we deduce the running mass m_b(m_b)=4234(56) MeV. The previous results are in good agreement with the ones from QCD spectral sum rules (QSSR) in full QCD to the same order [1]: f_B^qcd=206(7) MeV and m_b(m_b)^qcd=4236(69) MeV from the same channel. Using in addition the value m_b(m_b)=4177(11) MeV from the \Upsilon sum rules to order alpha_s^3 [2], we deduce the final averaged estimate from QSSR: f_B^qssr=204(6) MeV and m_b(m_b)^qssr=4181(11) MeV.

View original: http://arxiv.org/abs/1212.5544