Abstract

Motivated by the recent lattice study by FASTSUM collaboration, effective masses of the baryon parity-doublers are shown for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice Quantum Chromodynamics (QCD) observation, whereas the hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with the heavy pion comparable to the kaon. As an application to hot QCD, we demonstrate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Confronting the baryon number susceptibility, baryon–charge and baryon–strangeness correlations as well as their ratios with the lattice QCD data for the physical pion mass, we find that the strong downward mass shift in the hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations of lattice simulations. Another application of nucleon parity doubling is the physics of neutron stars. Under beta equilibrium and charge neutrality, hadronic matter with unbroken chiral symmetry can be favored in the core of the neutron stars.

Highlights

  • Spectral properties of hadrons are expected to change in a medium

  • The baryon octet and decuplet with opposite parity can be modeled in an effective chiral approach with N f = 2 + 1 [3], where the masses are described as certain functions of the light-quark σq and strange-quark σs condensates as well as the degenerate mass of parity doublers m0, which is not anchored to dynamical chiral symmetry breaking

  • Motivated by the recent lattice Quantum Chromodynamics (QCD) result on the baryon-octet and -decuplet masses at finite temperature, we formulated thermal masses of baryon parity doublers as functions of the chiral order parameter

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Summary

Introduction

Spectral properties of hadrons are expected to change in a medium. A search for those modifications because of partial restoration of the chiral symmetry has been one of the central subjects in heavy-ion collisions where hot and/or dense matter is supposed to be created. Substantial medium modifications of the lowest-lying hadrons have been predicted in a large class of chiral models, whereas their reliable estimates in lattice QCD are far limited to the screening masses. The obtained spectra follow qualitatively an expectation from parity doubling of the chiral symmetry, indicating that the states with the same spin but opposite parity tend to become degenerate when the symmetry gets partially restored. In this contribution, we briefly summarize our recent study on the thermodynamics of parity doubling: the in-medium masses of baryon octet and decuplet and their potential influence over fluctuations and correlations in the context of a chiral effective theory [3] and in-medium Hadron. Resonance Gas (HRG) model [4,5], as well as the physics of neutron stars in a hybrid approach for hadrons and quarks [6]

Parity Doubling
Fluctuations and Correlations
The Structure of Neutron Stars
Conclusions
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