Higher order net-baryon number cumulants and baryon-strangeness correlations: Comparing QCD results on the pseudo-critical line with RHIC-BES II results on the freeze-out line

Fakultät für Physik, Universität Bielefeld, Bielefeld, 33615, Germany

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Published online: 17 April 2026

Abstract

We present lattice QCD results for ratios of net-baryon number cumulants along the pseudo-critical line and compare them with STAR measurements from the RHIC BES-II program. The ratio of first and second order cumulants, R₁₂^B, agrees well with corresponding net-proton number cumulants down to √s_NN = 11.5 GeV or baryon chemical potentials μ_B/T ≤ 2. Likewise higher-order cumulant ratios, R₃₁^B and R₄₂^B, show no sign for the existence of a critical point in the parameter range explored with these cumulant ratios. A QCD critical point is unlikely to occur within the BES-II range in collider mode. Moreover, the results demonstrate that a non-interacting HRG description breaks down for μ_B/T > 1. We further analyze baryon-strangeness correlations normalized by strangeness fluctuations, finding consistency with STAR data at large beam energies but deviations at lower energies. Comparisons of electric-charge and strangeness correlations with STAR and ALICE data also show agreement at high energies, while the deviations at lower energies emphasize the role of unobserved strange resonances and the need for controlled feed-down corrections in baryon-strangeness correlations.