The measured partial widths of the semileptonic decays D to K l nu and D to
pi l nu can be combined with the form factors calculated on the lattice to
extract the CKM matrix elements |V_cs| and |V_cd|. The lattice calculations can
be checked by comparing the form factor shapes from the lattice and experiment.
We have generated a sizable data set by using heavy clover quarks with the
Fermilab interpretation for charm and asqtad staggered light quarks on 2+1
flavor MILC ensembles with lattice spacings of approximately 0.12, 0.09, 0.06,
and 0.045 fm. Preliminary fits to staggered chiral perturbation theory suggest
that we can reduce the uncertainties in the form factors at zero invariant mass
to below 5%.Comment: 7 pages, 4 figures, proceedings of the XXIX International Symposium
on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake
Tahoe, Californi