Universal relations between non-Gaussian fluctuations in heavy-ion collisions

Abstract

We show that universality near a critical end point implies a characteristic relation between third- and fourth-order baryon susceptibilities χ₃ and χ₄, resulting in a banana-shaped loop when χ₄ is plotted as a function of χ₃ along a freeze-out line. This result relies only on the derivative relation between χ₃ and χ₄, the enhancement of the correlation length and the scaling symmetry near a critical point, and the freeze-out line near the critical point not too parallel to the μ[subscript B] axis. Including the individual enhancements of χ₃ and χ₄ near a critical point, these features may be a consistent set of observations supporting the interpretation of baryon fluctuation data as arising from criticality.