Factorial cumulants of proton multiplicity near a critical point using maximum entropy freeze-out prescription

¹ Massachusetts Institute of Technology, Cambridge, MA 02139, USA
² University of Maryland, College Park, MD 20742 USA
³ University of Illinois, Chicago, Illinois 60607, USA
⁴ The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, China

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 17 April 2026

Abstract

We present the first application of the maximum-entropy freeze-out prescription to calculate factorial cumulants of proton multiplicities near the conjectured QCD critical point in thermal equilibrium. We use a parameterized class of possible EoS near QCD critical point, obtained via a mapping to the Gibbs free energy of the 3D Ising model. This equilibrium baseline highlights how factorial cumulants isolate critical fluctuations by subtracting trivial self-correlations, setting the stage for future out-of-equilibrium analyses. We identify the key nonuniversal aspects of the mapping to the Ising model that strongly control the characteristic properties, such as magnitude and location of the peaks of the factorial cumulants along the freeze-out curve.