A Comparative Study of fB within QCD Sum Rules with Two Typical Correlators up to Next-to-Leading Order

The B-meson decay constant f_B is an important component for studying the B-meson decays, which can be studied through QCD sum rules. We make a detailed discussion on f_B from two sum rules up to next-to-leading order, i.e. sum rules I and II, which are derived from the conventional correlator and the correlator with chiral currents respectively. It is found that these two sum rules are consistent with each other. The sum rules II involves less non-perturbative condensates as that of sum rules I, and in principle, it can be more accurate if we know the dimension-four gluon condensate well. It is found that f_B decreases with the increment of m_B, and to compare with the Belle experimental data on f_B, both sum rules I and II prefer smaller pole b-quarkmass, m_b=4.68±0.07 GeV. By varying all the input parameters within their reasonable regions and by adding all the uncertainties in quadrature, we obtain f_B=172^{+23}_{-25} MeV for sum rules I and f_B=214_{-34}^{+26} MeV for sum rules II.