The 10th International Workshop on Chiral Dynamics

The prospects and difficulties of computing nucleon-pion scattering amplitudes from lattice QCD simulations are illustrated with high-statistics results on a single ensemble of gauge field configurations with dynamical up, down, and strange quarks and a pion mass $m_\pi = 200{\rm MeV}$. The stochastic-LapH approach to quark propagation enables an efficient computation of all required correlation functions, and a good statistical precision is achieved for the $I=3/2$ amplitudes. The $I=1/2$ channel is considerably more difficult, complicating direct lattice determination of both scattering lengths.