Leptonic decay constants f_Ds and f_D in three flavor lattice QCD
  We determine the leptonic decay constants in three flavor unquenched lattice QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm quarks in the Fermilab heavy quark formalism. Our preliminary results, based upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is statistical while the is the combined systematic uncertainty. 
J.N. Simone, C. Aubin, C. Bernard, C. DeTar, M. di Pierro, A.X.   El-Khadra, Steven Gottlieb, E.B. Gregory, U.M. Heller, J.E...