Thermodynamic characterizations of exotic and missing states

TL;DR

This paper investigates the presence of exotic and missing hadronic states in QCD by analyzing thermodynamic fluctuations and entropy shifts within the Hadron Resonance Gas model, comparing results with lattice data.

Contribution

It introduces a method to identify exotic and missing states in QCD using thermodynamic observables and lattice data comparison.

Findings

Evidence for exotic hybrid states $g q ar q$ and $gqqq$ from entropy shift analysis.

Thermodynamic fluctuations can indicate the existence of missing states in the hadronic spectrum.

Abstract

Thermal shifts and fluctuations at finite temperature below the deconfinement crossover of QCD from hadronic matter to the Quark-Gluon Plasma provide a viable way to look for exotic and missing states with given quantum numbers in the hadronic spectrum. We study a realization of the Hadron Resonance Gas model in the light quark ($uds$) flavor sector of QCD to study: i) the entropy shifts, and ii) the fluctuations of electric charge, baryon number and strangeness; and extract from them the possible existence of missing and exotic states from a comparison with lattice data. The analysis of the entropy shift based on the free energy of the Polyakov loop suggests the existence of exotic hybrids $g q \bar q$ and $gqqq$.