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Thermodynamics and higher order moments in SU(3) linear $σ$-model with gluonic quasi-particles

In framework of linear $σ$-model (LSM) with three quark flavors, the chiral phase-diagram at finite temperature and density is investigated. At temperatures higher than the critical temperature ($ T_c $), we added to LSM the gluonic sector from the quasi-particle model (QPM), which assumes that the interacting gluons in the strongly interacting matter, the quark-gluon plasma (QGP), are phenomenologically the same as non-interacting massive quasi-particles. The dependence of the chiral condensates of strange and non-strange quarks on temperature and chemical potential is analysed. Then, we have calculated the thermodynamics in the new approach (combination of LSM and QPM). Confronting the results with recent lattice QCD simulations shows an excellent agreement in almost all thermodynamic quantities. The first and second order moments of particle multiplicity are studied in dependence on the chemical potential but at fixed temperature and on the chemical potential but at fixed temperature. These are implemented in characterizing the large fluctuations accompanying the chiral phase-transition. The results of first and second order moments are compared with the SU(3) Polyakov linear $σ$-model (PLSM). Also, the resulting phase-diagrams deduced in PLSM and LSM$+$QPM are compared with each other.