https://doi.org/10.1140/epjc/s10052-019-6703-x
Regular Article - Theoretical Physics
The kurtosis of net baryon number fluctuations from a realistic Polyakov–Nambu–Jona-Lasinio model along the experimental freeze-out line
1
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
2
School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
* e-mail: huangm@ucas.ac.cn
Received:
21
August
2018
Accepted:
19
February
2019
Published online:
18
March
2019
Firstly we qualitatively analyze the formation of the dip and peak structures of the kurtosis 
of net baryon number fluctuation along imagined freeze-out lines and discuss the signature of the existence of the QCD critical end point (CEP) in the Nambu–Jona-Lasinio (NJL) model, Polyakov-NJL (PNJL) model as well as 
-dependent PNJL( PNJL) model with different parameter sets, and then we apply a realistic PNJL model with parameters fixed by lattice data at zero chemical potential, and quantitatively investigate its along the real freeze-out line extracted from experiments. The important contribution from gluodynamics to the baryon number fluctuations is discussed. The peak structure of along the freeze-out line is solely determined by the existence of the CEP mountain and can be used as a clean signature for the existence of CEP. The formation of the dip structure is sensitive to the relation between the freeze-out line and the phase boundary, and the freeze-out line starts from the back-ridge of the phase boundary is required. To our surprise, the kurtosis produced from the realistic PNJL model along the experimental freeze-out line agrees with BES-I data well, which indicates that equilibrium result can explain the experimental data. It is worth to point out that the extracted freeze-out temperatures from beam energy scan measurement are indeed higher than the critical temperatures at small chemical potentials, which supports our qualitative analysis.
© The Author(s), 2019
