Nucleon-Pion Spectroscopy from Sparsened Correlators

Neutrino oscillation experiments require accurate reconstructions of neutrino energies, which depend in part on a theoretical understanding of the axial $N\to \mathrm{\Delta }$ transition form factors. Lattice QCD studies of this transition require construction of all hadronic states with energies up to the mass of the $\mathrm{\Delta }$ resonance, which includes $N\pi$ and $N\pi \pi$ for physical quark mass values. Building interpolating operators from sparse grids of source and sink points is a versatile method of approximating all-to-all quark propagators that has been successfully used in other multi-hadron calculations. This work will discuss applications of this method to $N\pi$ and $N\pi \pi$ systems and present preliminary results.