Speaker
Description
Recent intermediate-energy heavy-ion collision experiments are intensively examining the QCD phase diagram in search of critical signatures potentially linked to the QCD critical point. Such collisions generate a strongly interacting medium—or “fireball”—that exhibits pronounced inhomogeneities along the rapidity axis, thereby exploring a wide range of the QCD phase diagram simultaneously. This spatial variation creates an exceptional window to investigate critical phenomena in more detail. To leverage this feature, we go beyond the mid-rapidity region and consider higher-order cumulants of conserved charges across multiple rapidity intervals. This “rapidity scan” approach provides a novel complement to conventional beam energy scans.
To reliably identify critical signals, we must first establish a robust baseline that incorporates non-critical background effects. In this presentation, we detail our progress in constructing such a baseline for rapidity scans. Our analysis shows that baryon number conservation can create cumulant patterns resembling critical behavior, potentially causing misleading interpretations [1]. To address this challenge, we introduce a new class of observables—“cross-cumulants”—specifically tailored for rapidity scans. These observables retain sensitivity to genuine critical fluctuations while reducing the influence of conservation-driven backgrounds. With the aid of hydrodynamic simulations, we illustrate how cross-cumulants can discriminate between authentic critical signals and background-induced artifacts.
