Parity doubling of baryons in QCD thermodynamics

Motivated by the recent lattice study, thermal masses of the baryon parity-doublers are explored for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice QCD results, whereas hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with $m_{\pi }/m_K\sim 1$. We further investigate 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 correlation, and baryon-strangeness correlation and their ratios with the lattice QCD data, we show 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. This indicates that in order to correctly account for the influence of the chiral symmetry restoration on the fluctuation observables, a consistent framework of in-medium effects beyond hadron mass shifts is required.