Nucleon, $\Delta$ and $\Omega$ excited states in $N_f=2+1$ lattice QCD

TL;DR

This study uses lattice QCD to compute excited states of nucleons, deltas, and omegas with varying quark masses, employing the variational method and comparing results with experimental spectra.

Contribution

It introduces a comprehensive lattice QCD calculation of excited baryon states using a large operator basis and anisotropic lattices, highlighting the importance of multi-hadron operators.

Findings

Reasonable agreement with experimental spectra

Identification of multi-hadron state contributions

Effective use of variational method with large operator basis

Abstract

The energies of the excited states of the Nucleon, $\Delta$ and $\Omega$ are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculation is performed at three values of the light quark mass, corresponding to pion masses $m_{\pi}$ = 392(4), 438(3) and 521(3) MeV. We employ the variational method with a large basis of interpolating operators enabling six energies in each irreducible representation of the lattice to be distinguished clearly. We compare our calculation with the low-lying experimental spectrum, with which we find reasonable agreement in the pattern of states. The need to include operators that couple to the expected multi-hadron states in the spectrum is clearly identified.