Nucleon spectroscopy using multi-particle operators
The role of 5-quark operators in extracting the nucleon excited state spectrum via correlation matrix techniques is explored. In particular, the coupling of meson-baryon operators to nucleon resonance states and scattering states is studied. Results are presented for 2+1 flavour dynamical ensembles in both the positive and negative parity channels. Fitting a single-state ansatz to the eigenstate-projected correlators provides robust energies for the low-lying spectrum that are essentially invariant across a variety of different operator bases. In particular, the resonant state energies obtained both with and without the use of meson-baryon operators agree, demonstrating that resonance energies can be reliably extracted solely using 3-quark operators.