Net-baryon number fluctuations in the hybrid quark-meson-nucleon model at finite density

Abstract

We study the mean-field thermodynamics and the characteristics of the net-baryon number fluctuations at the phase boundaries for the chiral and deconfinement transitions in the Hybrid Quark-Meson-Nucleon model. The chiral dynamics is described in the linear sigma model, whereas the quark confinement is manipulated by a medium-dependent modification of the particle distribution functions, where an additional scalar field is introduced. At low temperature and finite baryon density, the model predicts a first-, second-order chiral phase transition, or a crossover, depending on the expectation value of the scalar field, and a first-order deconfinement phase transition. We focus on the influence of the confinement over higher-order cumulants of the net-baryon number density. We find that the cumulants show a substantial enhancement around the chiral phase transition, they are not as sensitive to the deconfinement transition.

Speed of sound and quark confinement inside neutron stars

“…This is particularly useful for determining a class of effective models in which the low-density and high-density regimes are not treated independently, but rather combined in a consistent unified framework. To this end, we employ the hybrid quark-meson-nucleon (QMN) model [25][26][27][28][29] to quantify the EoS of cold and dense matter under NS conditions. The model has the characteristic feature that, at increasing baryon density, the chiral symmetry is restored within the hadronic phase by lifting the mass splitting between chiral partner states, before the quark deconfinement takes place.…”

Parity Doubling and the Dense-Matter Phase Diagram under Constraints from Multi-Messenger Astronomy

“…The remaining parameters, g q , κ b , and λ b , do not depend on the choice of m 0 , and their values are taken from Ref. [17]. and neutral N(938) states, i.e., proton (p + ) and neutron (n + ), respectively.…”

Parity Doubling in QCD Thermodynamics

“…We recently applied the chiral effective model with nucleon parity doubling to the physics of neutron stars under β equilibrium and charge neutrality [6]. We utilize a hybrid model where both quarks and hadrons are treated as dynamical degrees of freedom together with a mechanism to suppress the quarks (nucleons) at low (high) density [11,12]. The model yields the chiral symmetry restoration as a first-order, a second-order phase transition or a smooth crossover, depending on two major parameters; one is the degenerate mass of nucleon parity doublers with restored chiral symmetry, m 0 , and the other is the infra-red cutoff of the quark thermal distribution function in matter-free space, αb 0 [11].…”