Meson and baryon spectrum for QCD with two light dynamical quarks

TL;DR

This study investigates the meson and baryon spectrum in lattice QCD with two light dynamical quarks, providing insights into ground and excited states, including spin-two mesons and strange hadrons, using variational methods.

Contribution

The paper presents new lattice QCD results on meson and baryon spectra with dynamical quarks, including excited states and scattering considerations, using the Chirally Improved Dirac operator.

Findings

Ground states are determined with high precision.

Radial excitations are identified in multiple channels.

Finite size effects impact excited baryon results.

Abstract

We present results of meson and baryon spectroscopy using the Chirally Improved Dirac operator on lattices of size 16**3 x 32 with two mass-degenerate light sea quarks. Three ensembles with pion masses of 322(5), 470(4) and 525(7) MeV and lattice spacings close to 0.15 fm are investigated. Results on ground and excited states for several channels are given, including spin two mesons and hadrons with strange valence quarks. The analysis of the states is done with the variational method, including two kinds of Gaussian sources and derivative sources. We obtain several ground states fairly precisely and find radial excitations in various channels. Excited baryon results seem to suffer from finite size effects, in particular at small pion masses. We discuss the possible appearance of scattering states in various channels, considering masses and eigenvectors. Partially quenched results in the scalar channel suggest the presence of a 2-particle state, however, in most channels we cannot identify them. Where available, we compare our results to results of quenched simulations using the same action.