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.
Nuclear
Physics Colloquium