Nucleon spectroscopy using multi-particle operators

TL;DR

This paper investigates the effectiveness of multi-particle operators, especially meson-baryon operators, in extracting the nucleon excited state spectrum, demonstrating that resonance energies can be reliably obtained with 3-quark operators alone.

Contribution

It shows that resonance energies in nucleon spectroscopy can be accurately determined without meson-baryon operators, using only 3-quark operators, across various operator bases.

Findings

Resonance energies are consistent with and without meson-baryon operators.

Single-state fits yield robust energies for low-lying states.

Resonance energies are invariant across different operator bases.

Abstract

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.