Fluctuation Probes of QCD Matter in Heavy-Ion Collisions

Abstract

This talk explores fluctuation probes of QCD matter generated in heavy-ion collisions at RHIC and LHC. First, the RHIC-BES-II data on proton cumulants is examined within the framework of hydrodynamic calculations and in the context of QCD critical point expectations. We elaborate on the properties of appropriately scaled factorial cumulants and how acceptance dependence analysis can illuminate the presence of short- and long-range correlations. Challenges in simultaneously describing protons and antiprotons will be emphasized, highlighting what the differences between the two can reveal about the thermalization of the system. In the second part of the talk, the topic of net-charge fluctuations as an indicator of fractional quark charges will be revisited. Utilizing a novel approach for describing 2-point charge density correlations, we perform a quantitative analysis of LHC measurements, which reveals moderate evidence for the freeze-out of charge fluctuations taking place in the QGP.