Abstract
We investigate the kurtosis and skewness of net-baryon number fluctuations in the Polyakov loop extended Nambu–Jona-Lasinio (PNJL) model, and discuss the relations between fluctuation distributions and the phase structure of quark-gluon matter. The calculation shows that the traces of chiral and deconfinement transitions can be effectively reflected by the kurtosis and skewness of net-baryon number fluctuations not only in the critical region but also in the crossover region. The contour plot of baryon number kurtosis derived in the PNJL model can qualitatively explain the behavior of net-proton number kurtosis in the STAR beam energy scan experiments. Moreover, the three-dimensional presentations of the kurtosis and skewness in this study are helpful to understand the relations between baryon number fluctuations and QCD phase structure.
Highlights
The exploration of QCD phase diagram and search for phase transition signatures of strongly interacting matter are subjects of great interest in high energy nuclear physics
We for the first time display the three-dimensional diagrams of kurtosis and skewness of net-baryon fluctuations in the Polyakov loop extended Nambu–Jona-Lasinio (PNJL) model. These diagrammatic presentations are very helpful to understand the relations between baryon number fluctuation distributions and QCD phase structure
The calculation indicates that the QCD phase structure is mainly determined by the chiral and deconfinement transitions, as well as their coincidence and separation
Summary
The exploration of QCD phase diagram and search for phase transition signatures of strongly interacting matter are subjects of great interest in high energy nuclear physics. The preliminary result of the first phase of STAR Beam Energy Scan (BES-I) in Au+Au collisions indicates that the kurtosis of net-proton number fluctuation presents a non-monotonic energy dependence and a large deviation from the Poisson baseline [36,37,38] This phenomenon can be qualitatively explained in the σ field model with a critical fluctuation of a first-order phase transition [27]. We for the first time display the three-dimensional diagrams of kurtosis and skewness of net-baryon fluctuations in the PNJL model These diagrammatic presentations are very helpful to understand the relations between baryon number fluctuation distributions and QCD phase structure.
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