QCD with Two Light Dynamical Chirally Improved Quarks: Baryons

TL;DR

This study investigates baryon ground states and excitations using lattice QCD with dynamical Chirally Improved quarks, providing results that generally align with experimental data and offering insights into flavor symmetry contributions.

Contribution

First lattice QCD study of baryon spectra with Chirally Improved quarks across multiple ensembles and volumes, including infinite volume extrapolation.

Findings

Results agree with experimental baryon masses in the infinite volume limit.

Identified flavor symmetry contributions in baryon eigenstates.

Observed discrepancies in some excited states compared to quark model expectations.

Abstract

We present a study of baryon ground states and low lying excitations of non-strange and strange baryons. The results are based on seven gauge field ensembles with two dynamical light Chirally Improved (CI) quarks corresponding to pion masses between 255 and 596 MeV and a strange valence quark with mass fixed by the Omega baryon. The lattice spacing varies between 0.1324 and 0.1398 fm. Given in lattice units, the bulk of our results are for size 16^3\times 32, for two ensembles with light pion masses (255 and 330 MeV) we also use 24^3\times 48 lattices and perform an infinite volume extrapolation. We derive energy levels for the spin 1/2 and 3/2 channels for both parities. In general, our results in the infinite volume limit compare well with experiment. We analyze the flavor symmetry content by identifying the singlet/octet/decuplet contributions of the resulting eigenstates. The ground states compositions agree with quark model expectations. In some cases the excited states, however, disagree and we discuss possible reasons.