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Analysis of the decay constants of the heavy pseudoscalar mesons with QCD sum rules

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 $α_s<\bar{q}q>$ and partial one-loop corrections to the four-quark condensates $α_s^2<\bar{q}q>^2$, 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 $m=m(μ)$ and take perturbative corrections up to the order $\mathcal{O}(α_s)$; {\bf II} we choose the pole masses $m$, take perturbative corrections up to the order $\mathcal{O}(α_s^2)$ and set the energy-scale to be the heavy quark pole mass $μ=m_Q$. 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.