Disentangling equation of state and canonical ensemble effects on proton fluctuations via a density correlations formalism

Measurements of proton number fluctuations in heavy-ion collisions are a key probe in the search for the QCD critical point. State-of-the-art hydrodynamic simulations that incorporate net-baryon conservation and repulsive interactions provide a noncritical baseline for these observables. We re-evaluate proton cumulants using a density correlations formalism, clarify its relationship to the subensemble acceptance method (SAM), and isolate the respective impacts of the equation of state, kinematic acceptance, and exact conservation (canonical ensemble). We compare our calculations with measurements from the RHIC Beam Energy Scan and assess potential indications of critical behavior.