Quenched heavy-light decay constants

We present results for heavy-light decay constants, using both propagating quarks and the static approximation, in $O\left(a\right)\mathrm{}$-improved, quenched lattice QCD. At $\beta =6.2\mathrm{}$ on a ${24}^3$×48 lattice we find $f_D={185}_{-3\mathrm{}}^{+4\mathrm{}}{\left(\mathrm{stat}\right)}_{-7\mathrm{}}^{+42\mathrm{}}\left(\mathrm{syst}\right)$ MeV, $f_B={160}_{-6-19\mathrm{}}^{+6+53\mathrm{}}$ MeV, $\frac{f_{D_s}}{f_D}={1.18}_{-2\mathrm{}}^{+2\mathrm{}}$, and $\frac{f_{B_s}}{f_B}={1.22}_{-3\mathrm{}}^{+4\mathrm{}}$, in good agreement with earlier studies. From the static theory we obtain $f_B^{\mathrm{stat}}={253}_{-15-15\mathrm{}}^{+16+105\mathrm{}}$ MeV. We also present results from a simulation at $\beta =6.0\mathrm{}$ on a ${16}^3$×48 lattice, which are consistent with those at $\beta =6.2\mathrm{}$. In order to study the effects of improvement, we present a direct comparison of the results using both the Wilson and the improved action at $\beta =6.0\mathrm{}$.