Alladi Ramakrishnan Hall

Quantifying fluctuation signatures near critical point using maximum entropy freeze-out

Maneesha Sushama Pradeep

Maryland University

A key question about the QCD phase diagram is whether there is a critical point somewhere on the boundary between the hadron gas and quark-gluon plasma phases, and
if so where. Heavy-ion
collisions offer a unique opportunity to search for signatures of such a critical point by analyzing event-by-event fluctuations in particle multiplicities. To draw meaningful conclusions from experimental data,  a theoretical framework is needed to link QCD thermodynamics with the particle spectra and correlations
observed in detectors. This is done in the least biased by maximizing the entropy associated with the hadron resonance gas ensemble, subject to matching conditions
from the hydrodynamic description at freeze-out. We use maximum entropy freeze-out of fluctuations to make estimates for the factorial cumulants of proton
multiplicities, assuming thermal equilibrium, for a family of EoSs with a 3D Ising-like critical point, varying the microscopic inputs that determine the location
and strength of the critical point. The unknown Equation of State (EoS) of QCD near a critical point can be related to the universal Gibbs free energy of the 3D
Ising model using four non-universal mapping parameters whose values are determined by the microscopic details of QCD. We quantify the effect of the non-universal
mapping parameters, and the distance between the critical point and the freeze-out curve, on the factorial cumulants of proton multiplicities.