The behavior of strange matter in the frame of the SU(3)Polyakov-loop extended Nambu-Jona-Lasinio model including $U_A(1)$ anomaly is considered. We discuss the appearance of a peak in the ratio of the number of strange mesons to non-strange mesons known as the horn. The PNJL model gives a schematic description of the chiral phase transition and meson properties at finite temperature and density. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density. This may explain the difference in the $K^+/pi^+$ ratio and $K^-/pi^-$ ratio at low $sqrt{s_{NN}}$ and their tendency to the same value at high $sqrt{s_{NN}}$. We also show that the rise in the ratio $K^+/pi^+$ appears near CEP when we build the $K^+/pi^+$ ratio along the phase transition diagram and it can be considered as a critical region signal.
Download