The Positive-Parity Baryon Spectrum and the Role of Hybrid Baryons

TL;DR

This study computes the positive-parity baryon spectrum using lattice QCD at two pion masses, revealing the presence of hybrid states with gluonic contributions, consistent across different lattice actions.

Contribution

It demonstrates the identification of hybrid baryons in the spectrum using a generalized variational method within the distillation framework, independent of lattice details.

Findings

Spectrum matches features from previous lattice calculations.

Hybrid states with gluonic degrees of freedom are observed.

Hybrid states are a universal feature of excited baryons.

Abstract

We calculate the low-lying spectra for the positive-parity $\Delta$ and $N$ at two pion masses of 358 and 278 MeV using an isotropic clover action with two degenerate light-quaark and one strange-quark flavors through the application of the generalized variational method within the distillation framework. The spectrum exhibits the general features observed in previous calculations using an anisotropic clover lattice, with a counting of states at least as rich as the quark model. Furthermore, we identify states that are hybrid in nature, where gluonic degrees of freedom play a structural role, indicatinng that such states appear a feature of the excited baryon spectrum, irrespective of the lattice action, or the precise details of the smearing of the lattice interpolating operators used to identify such states.