Post date: Aug 25, 2010 7:40:41 AM
I have a new paper out (with the HPQCD collaboration) on a lattice QCD
calculation of the F_Ds decay constant.
We update our previous determination of both the decay constant and the mass of the $D_s$ meson using the Highly Improved Staggered Quark formalism. We include additional results at two finer values of the lattice spacing along with improved determinations of the lattice spacing and improved tuning of the charm and strange quark masses. We obtain $m_{D_s}$ = 1.9691(32) GeV, in good agreement with experiment, and $f_{D_s}$ = 0.2480(25) GeV. Our result for $f_{D_s}$ is 1$\sigma$ lower than recent experimental results determined from the $D_s$ leptonic decay rate and using $V_{cs} = V_{ud}$. Combining our $f_{D_s}$ with the experimental rate we obtain a direct determination of $V_{cs} = 1.009(27)$, or alternatively $0.988 {+0.015 \atop -0.018}$ using a probability distribution for statistical errors for this quantity which vanishes above 1. We also include an accurate prediction of the decay constant of the $\eta_c$, $f_{\eta_c}$ = 0.3947(24) GeV, as a calibration point for other lattice calculations.