A recent study has investigated net-baryon number fluctuations in the quantum chromodynamics (QCD) phase diagram, focusing on the high-density, low-temperature region. Using the parity-doublet model (PDM) under the mean-field approximation, researchers calculated fluctuation ratios up to sixth order. These high-order fluctuations are particularly sensitive to the nuclear liquid-gas phase transition, a crucial phenomenon for understanding the behavior of nuclear matter under extreme conditions.

To connect these theoretical results with heavy-ion experiments, the team explored several chemical freeze-out scenarios. They found that the extracted fluctuations near the liquid-gas transition strongly depend on the choice of the freeze-out curve. The researchers self-consistently determined four freeze-out points from preliminary results of the STAR Collaboration, enabling a direct comparison between the model and experimental data.

By comparing experimental data with PDM results at these four points, the model adequately describes low-energy data (center-of-mass collision energies per nucleon, √sNN ≲ 4 GeV). This finding suggests that nucleonic interactions and the liquid-gas phase transition itself may significantly contribute to the fluctuations observed in low-energy heavy-ion collisions. The research opens new avenues for exploring the QCD phase diagram and better understanding the fundamental properties of nuclear matter.