Charmed meson spectra and decay constants with one-loop $O(a)$ improved   relativistic heavy quark action
  We calculate charmed meson spectra and decay constants in lattice QCD employing one-loop $O(a)$ improved heavy quark action and axial-vector currents. In quenched simulations at $a \sim 0.1$ fm with the plaquette gauge action as well as a renormalization-group improved one, it is shown that the deviation from the continuum dispersion relation and the violation of space-time symmetry for the pseudoscalar meson decay constants are substantially reduced, once the $O(a)$ improvement is applied. Preliminary results with two flavors of dynamical quarks are also presented. 
Y. Kayaba, S. Aoki, M. Fukugita, K-I. Ishikawa, Y. Iwasaki, K. Kanaya,   T. Kaneko, Y. Kuramashi, M. Okawa, A. Ukawa, T. Yos...