The QCD phase diagram and the baryon number fluctuations in NJL model with a temperature damping coupling strength

Abstract We investigate the chiral phase diagram in the NJL model with a modified coupling strength. Moreover, we delve deeply into the fluctuations of baryon numbers. A temperature damping factor for the coupling strength is introduced to mimic the temperature dependence of quantum chromodynamics (QCD) in the low and middle temperature ranges. This novel parameter is fitted by using the quark condensate from lattice QCD at finite temperature. Our approach provides a significant enhancement to the chiral phase diagram, accurately reproducing the pseudocritical temperature at μ B = 0 and aligning the crossover boundary with lattice QCD results. The quark condensate is used to ascertain the location of the phase transition, and we find an area where both phases coexist. The chiral susceptibility is employed to identify the pseudo-critical line in the crossover region. The skewness ratios and the kurtosis ratios varying with T at several different μ B are calculated meticulously, and the results demonstrate that they experience a significant change around the pseudo-critical line. Additionally, the skewness ratios and the kurtosis ratios along the pseudo-critical line ( T c ( μ B )) and the lines deviating from T c ( μ B ) are computed to gain a better understanding of the experimental results. This implies that the freeze-out line is relatively far from the critical end point.