Towards a determination of the spectrum of QCD using a space-time lattice

TL;DR

This paper discusses progress in calculating the QCD resonance spectrum using lattice Monte Carlo methods, emphasizing operator construction, smearing techniques, and energy level extraction.

Contribution

It introduces improved operator and smearing techniques for more accurate determination of baryon and meson spectra on space-time lattices.

Findings

Successfully extracted nine energy levels in a symmetry channel

Highlighted importance of extended operators for baryon structure

Demonstrated methods for identifying continuum spin quantum numbers

Abstract

Progress by the Lattice Hadron Physics Collaboration in determining the baryon and meson resonance spectrum of QCD using Monte Carlo methods with space-time lattices is described. The extraction of excited-state energies necessitates the evaluation of correlation matrices of sets of operators, and the importance of extended three-quark operators to capture both the radial and orbital structures of baryons is emphasized. The use of both quark-field smearing and link-field smearing in the operators is essential for reducing the couplings of the operators to the high-frequency modes and for reducing statistical noise in the correlators. The extraction of nine energy levels in a given symmetry channel is demonstrated, and identifying the continuum spin quantum numbers of the levels is discussed.