In this article, we recalculate the contributions of all vacuum condensates up to dimension-6, in particular the one-loop corrections to the quark condensates $\alpha_s<\bar{ q}q>$ and partial one-loop corrections to the four-quark condensates $\alpha_s^2<\bar{ q}q>^2$, in the operator product expansion. Then we study the masses and decay constants of the heavy pseudoscalar mesons $D$, $D_s$, $B$ and $B_s$ using the QCD sum rules with two choices: { \bf I} we choose the $\bar{ MS}$ masses by setting $m=m(\mu)$ and take perturbative corrections up to the order $\mathcal{ O}(\alpha_s)$; { \bf II} we choose the pole masses $m$, take perturbative corrections up to the order $\mathcal{ O}(\alpha_s^2)$ and set the energy-scale to be the heavy quark pole mass $\mu=m_Q$. In the case of { \bf I}, the predictions $f_D=(208\pm11)\,\rm{ MeV}$ and $f_B=(189\pm15)\,\rm{ MeV}$ are consistent with the experimental data within uncertainties, while the prediction $f_{ D_s}=(241\pm12)\,\rm{ MeV}$ is below the lower bound of the experimental data $f_{ D_s}=(260.0\pm5.4)\,\rm{ MeV}$. In the case of { \bf II}, the predictions $f_D=(211\pm14)\,\rm{ MeV}$, $f_B=(190\pm17)\,\rm{ MeV}$, $f_{ D_s}=(258\pm13)\,\rm{ MeV}$ and $f_{ D_s}/f_D=1.22\pm0.08$ are all in excellent agreements with the experimental data within uncertainties.
Categories: hep-ph hep-ex