Charmed meson decay constants in three-flavor lattice QCD
  We present the first lattice QCD calculation with realistic sea quark content of the D^+ meson decay constant f_{D^+}. We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f_{D^+} = 201 +/- 3 +/- 17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f_{D_s} = 249 +/- 3 +/- 16 MeV for the D_s meson. 
C. Aubin, C. Bernard, C. DeTar, M. Di Pierro, E. D. Freeland, Steven   Gottlieb, U. M. Heller, J. E. Hetrick, A. X. El-Khadr...