The SU(3)-breaking effects in the leading and subleading parameters appearing in the heavy quark expansion of decay constants of the heavy-light mesons are systematically analyzed to two loop accuracy using QCD sum rules. We find that the SU(3)-breaking effects in the decay constant of the pseudoscalar are, respectively, about 20% for the b-flavored meson, 17% for the charmed meson, i.e., ${\mathit{f}}_{{\mathit{B}}_{\mathit{s}}}$/${\mathit{f}}_{\mathit{B}}$=1.20±0.04±0.03,${\mathit{f}}_{{\mathit{D}}_{\mathit{s}}}$/${\mathit{f}}_{\mathit{D}}$=1.17±0 .03±0.03 (the first error comes from the sum rule uncertainty, the second one from the uncertainty in the strange quark mass) and, in the expansion of ${\mathit{f}}_{{\mathit{P}}_{\mathit{s}}}$√${\mathit{m}}_{{\mathit{P}}_{\mathit{s}}}$/${\mathit{f}}_{\mathit{P}}$√${\mathit{m}}_{\mathit{P}}$, the subleading order is about -3% of the corresponding leading one for the b-flavored meson, about -5.5% for the charmed meson, and depends on the strange quark mass very weakly. In addition, the ratios of the vector to pseudoscalar meson decay constants are found to be ${\mathit{f}}_{{\mathit{B}}_{\mathit{s}}^{\mathrm{*}}}$/${\mathit{f}}_{{\mathit{B}}_{\mathit{s}}}$=${\mathit{f}}_{{\mathit{B}}^{\mathrm{*}}}$/${\mathit{f}}_{\mathit{B}}$=1.05±0.02 *0.00, and the SU(3)-breaking effect in the mass is about 102±16±20 MeV. © 1996 The American Physical Society.

• Received 31 July 1995

DOI:https://doi.org/10.1103/PhysRevD.53.5042