The pion nucleon sigma term with dynamical Wilson fermions a feasibility study

In a full QCD lattice study with Nf = 2 Wilson fermions, we seek to optimize the signals for the disconnected contributions to the Pion Nucleon Sigma term σN. We demonstrate, in form of a numerical analysis, that — in order to achieve a tolerable signal to noise-ratio in full QCD - it is advantageous to work with a Z2-noise source rather than to use Gaussian noise sources or to rely only on gange invariance to cancel non-gauge-invariant background. We find that 10 Z2-noise sources suffice on our sample (about 150 independent QCD configurations at β = 5.6 on 163 × 32 with κsea = 0.157, equivalent to MπMϱ = 0.7(1), to achieve decent signals and adequate fluctuations, rather than 300 such sources as recently used in quenched simulations.