Effect of H^pm on D^pm_sto μ^pmν and D^pm_sto τ^pmν

We investigate the effect of a charged Higgs boson (H^\pm) on the decays D^\pm_s\to \mu^\pm\nu and D^\pm_s\to \tau^\pm\nu, which will be measured with high precision at forthcoming CLEO-c. We show that a H^\pm can suppress the branching ratios by 10% \to 15% from the Standard Model prediction, and we emphasize that such contributions should not be overlooked when comparing lattice calculations of f_{D_s} to the values obtained from these decays.