Robust characteristics of nongaussian fluctuations from the NJL model

TL;DR

This paper investigates higher-order baryon, charge, and strangeness susceptibilities near a chiral critical point using the NJL model, revealing robust qualitative behaviors and implications for experimental freeze-out conditions.

Contribution

It provides a detailed analysis of susceptibilities near the critical point within the NJL model, highlighting their qualitative robustness and quantitative differences for various conserved charges.

Findings

Baryon number fluctuations are the largest and most detectable signal.

Charge and strangeness susceptibilities diverge at the critical point but require closer freeze-out proximity.

Susceptibilities exhibit non-monotonic behavior along freeze-out lines.

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 third- and fourth-order susceptibilities against each other along the freeze-out line exhibits clearly their non-montonicity and robust features.