Scattering in the πN negative parity channel in lattice QCD

We study the coupled pi N system (negative parity, isospin 1/2) based on a lattice QCD simulation for n(f) = 2 mass degenerate light quarks. Both standard 3-quark baryon operators as well as meson-baryon (4 + 1)-quark operators are included. This is an exploratory study for just one lattice size and lattice spacing and at a pion mass of 266 MeV. Using the distillation method and variational analysis we determine energy levels of the lowest eigenstates. Comparison with the results of simple 3-quark correlation studies exhibits drastic differences and a new level appears. A clearer picture of the negative parity nucleon spectrum emerges. For the parameters of the simulation we may assume elastic s-wave scattering and can derive values of the phase shift. DOI: 10.1103/PhysRevD.87.054502