2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/193734We present the first 2+1 flavour lattice QCD calculations of pseudoscalar flavour-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.44 pages,24 FiguresHigh Energy Physics - Latticetext