Constraints on the hadronic spectrum from Lattice QCD

TL;DR

This paper investigates how the hadronic spectrum influences lattice QCD results and proposes new observables to determine the necessity of including additional states for better theoretical and experimental agreement.

Contribution

It introduces novel observables sensitive to spectrum content, aiding in identifying which and how many new hadronic states should be included in models.

Findings

New observables effectively differentiate spectrum contributions.

Comparison clarifies the spectrum content needed for accurate modeling.

Results guide the inclusion of additional states in hadronic models.

Abstract

The spectrum of hadronic resonances continually receives updates from the Particle Data Group, which lists every state with a status representing how established the state is. Moreover, the existence of additional states is predicted by relativistic quark models. It has been suggested that further states might need to be included in the hadronic spectrum in order to improve the agreement between the hadron resonance gas model predictions and lattice QCD data. Such an inclusion would also affect the results of many areas of heavy-ion collision physics that make use of hadronic degrees of freedom, such as hydrodynamical simulations afterburners. However, for some selected observables, the inclusion of further states worsens the agreement with the lattice results. We propose new observables, sensitive to the spectrum content divided by quantum numbers, which allow us to gauge the contribution of additional states. The comparison of Lattice QCD results and predictions from the Hadron Resonance Gas model for these observables, helps to clarify the situation and determine how many, and which new states are needed.