We use an improved version of the $SU(3)$ flavour parity doublet quark-hadron model to investigate the baryon number susceptibilities near the de-confinement and nuclear liquid-gas transition. The parity doublet model has been improved by adding the six-point interaction of the $\sigma$ (and $\zeta$) meson in the effective mean field Lagrangian, resulting in a good description of nuclear ground-state properties, in particular the nuclear compressibility. The resulting phase diagram of the model agrees qualitatively with expectations from lattice QCD, i.e. it shows a crossover at zero net baryo-chemical potential and a critical point at finite density. Using this model we investigate the dependence of the higher order baryon number susceptibilities as function of temperature and chemical potential. Due to the interplay between the de-confinement and nuclear liquid-gas transition, the experimentally measured cumulants of the net baryon number may show very different beam energy dependence depending on the actual freeze-out temperature.
|Preferred Track||Correlations and Fluctuations|