Decay Constants of Heavy-Light Mesons

The decay constants of the heavy-light pseudoscalar mesons are studied in a high statistics run using the Wilson action at $\beta =6.0$ and $\beta =6.2$, and the clover action at $\beta =6.0$. The systematics of $O(a)$ discretisation errors are discussed. Our best estimates of the decay constants are: $f_D$ = 218(9) MeV, $f_D\mathrm{/}{f}_{Ds}$ = 1.11(1) and we obtain preliminary values for $f_B$.