Nucleon excited states on the lattice

TL;DR

This study uses lattice QCD simulations to analyze nucleon excited states and pion-nucleon interactions, revealing the impact of two-particle states on energy levels and exploring resonance properties.

Contribution

It introduces a detailed lattice QCD analysis of nucleon excited states with two-particle state inclusion and phase shift extraction methods.

Findings

Including two-particle states significantly alters energy levels.

Variational analysis and distillation are crucial for accurate energy extraction.

Phase shift analysis provides insights into resonance characteristics.

Abstract

We study the pion-nucleon system in s-wave in the framework of lattice QCD in order to gain new information on the nucleon excited states. We perform simulations for $n_f =2$ mass degenerate light quarks at a pion mass of 266 MeV. The results show that including the two-particle states drastically changes the energy levels. The variational analysis and the distillation approach play an important role in the extraction of the energy levels. The phase shift analysis allows to extract information on the resonance nature of the observed states.