Meson spectroscopy from spectral densities in lattice gauge theories

TL;DR

This paper develops and tests new computational methods to extract spectral densities from lattice gauge theory data, enabling detailed analysis of meson spectra relevant for both standard and beyond-standard physics.

Contribution

It introduces new software and optimized techniques for reconstructing spectral densities from lattice data, applicable to various gauge theories including QCD.

Findings

Successfully reconstructed meson spectral densities from lattice data.

Optimized smearing parameters improve spectral density analysis.

Generated new lattice ensembles with extended temporal dimensions.

Abstract

Spectral densities encode non-perturbative information that enters the calculation of a plethora of physical observables in strongly coupled field theories. Phenomenological applications encompass aspects of standard-model hadronic physics, observable at current colliders, as well as correlation functions characterizing new physics proposals, testable in future experiments. By making use of numerical data produced in a Sp(4) lattice gauge theory with matter transforming in an admixture of fundamental and 2-index antisymmetric representations of the gauge group, we perform a systematic study to demonstrate the effectiveness of recent technological progress in the reconstruction of spectral densities. To this purpose, we write and test new software packages that use energy-smeared spectral densities to analyze the mass spectrum of mesons. We assess the effectiveness of different smearing kernels and optimize the smearing parameters to the characteristics of available lattice ensembles. We generate new ensembles for the theory in consideration, with lattices that have a longer extent in the time direction with respect to the spatial ones. We run our tests on these ensembles, obtaining new results about the spectrum of light mesons and their excitations. We make available our algorithm and software for the extraction of spectral densities, that can be applied to theories with other gauge groups, including the theory of strong interactions (QCD) governing hadronic physics in the standard model.