We present the first $2+1$ flavor lattice QCD calculations of pseudoscalar flavor-singlet propagators using improved staggered fermions. We explore the relevant techniques and discuss prospects for the larger scale studies now in progress. The disconnected correlator is shown to have a highly non-Gaussian distribution and reliable estimates of the errors require care.

• Received 9 October 2007

DOI:https://doi.org/10.1103/PhysRevD.77.065019