Lattice QCD determination of patterns of excited baryon states

TL;DR

This paper uses lattice QCD to compute energies of excited baryon states, revealing patterns consistent with physical states and decomposing higher spin states for the first time.

Contribution

It introduces a novel lattice QCD method to analyze higher spin excited baryons using nonlocal operators and octahedral group representations.

Findings

Patterns of degenerate energies match physical state predictions

First decomposition of spin 5/2 or higher states in lattice QCD

Low-lying excited states align with continuum spin patterns

Abstract

Energies for excited isospin I=1/2 and I=3/2 states that include the nucleon and Delta families of baryons are computed using quenched, anisotropic lattices. Baryon interpolating field operators that are used include nonlocal operators that provide G_2 irreducible representations of the octahedral group. The decomposition of spin 5/2 or higher spin states is realized for the first time in a lattice QCD calculation. We observe patterns of degenerate energies in the irreducible representations of the octahedral group that correspond to the subduction of the continuum spin 5/2 or higher. The overall pattern of low-lying excited states corresponds well to the pattern of physical states subduced to the irreducible representations of the octahedral group.