Robust characteristics of non-Gaussian fluctuations from the NJL model

Abstract

We evaluate the third-and fourth-order baryon, charge and strangeness susceptibilities near a chiral critical point using the Nambu-Jona-Lasinio model. We identify robust qualitative behaviours of the susceptibilities along hypothetical freeze-out lines that agree with previous model studies. Quantitatively, baryon number fluctuations are the largest in magnitude and thus offer the strongest signal when freeze-out occurs farther away from a critical point. Charge and strangeness susceptibilities also diverge at a critical point, but the area where the divergence dominates is smaller, meaning freeze-out must occur closer to a critical point for a signal to be visible in these observables. In case of strangeness, this is attributable to the relatively large strange quark mass. Plotting the thirdand fourth-order susceptibilities against each other along the freeze-out line exhibits clearly their non-montonicity and robust features.

Impact of resonance decays on critical point signals in net-proton fluctuations

“…(10). A different NJL model study [65] shows that the baryon skewness is negative on the high (μ B , T ) side of the transition line. Again, this result corresponds to changing one of the signs in our model.…”

“…The skewness is an odd function of h, cf. also [15,37], which is positive for h < 0 and changes sign continuously (discontinuously) for positive (negative) r when h becomes positive. The kurtosis, instead, is an even function of h, which for a given r > 0 is negative within an interval |h| < h * (r ) which depends on r .…”

“…from appropriate derivatives of M with respect to the classical field keeping r fixed [14,15,37]. A parametric representation of M based on [46] can be found in Appendix A.…”

“…Promising observable signatures for the presence of a critical point include event-by-event fluctuations [5][6][7], in particular fluctuations of conserved quantum numbers such as baryon number or electric charge [8,9]. The influence of a phase transition, or a change of its order, should be reflected in a non-monotonic √ s-dependence of these a e-mail: mbluhm@ncsu.edu observables [10][11][12][13][14][15]. Moreover, non-uniform structures in e.g.…”

Baryon number fluctuations and the phase structure in the PNJL model

“…The baryon number fluctuations are investigated recently in different models, for example, the NJL model [39,40], the Polyakov Loop extended Quark Meson model [41], the functional renormalization group approach [42], the DSE approach [18], the interacting hadronic model [43,44] and the holographic QCD model [45]. Up to now the interpretation of the experimental results remains controversial [28][29][30][31]39,41,43,44] and phase transformation mechanism leading to the non-monotonic energy dependence of net proton kurtosis is still not clear.…”