  Accurately calculating the mass of flavor-singlet meson states from numerical
lattice simulations is an important milestone for lattice QCD. Careful
measurement of the full pseudoscalar flavor-singlet propagator is also a
crucial step in understanding the dynamics of the fermion sea on the lattice,
in particular for potentially non-trivial formulations such as with 2+1-flavor
staggered fermions. We briefly describe details of a dynamical QCD calculation
using improved staggered fermions, with 30,000 trajectories, that was run for
our studies of flavour singlet mesons.
