Quenched chiral perturbation is used to study the decay constants for heavy-light mesons beyond the leading order in 1/M. The results are used to estimate the error in quenched lattice calculations of the decay constants. For the double ratio $R_1 = ( f_{ D_s}/f_D) / (f_{ B_s}/f_B)$ we find that the error is small, conservatively 6%, but likely smaller. We also find that quenching decreases the ratio $f_{ D_s}/f_D$ relative to the unquenched theory.
Categories: hep-ph