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

TL;DR

This study uses lattice QCD to analyze higher-order baryon number cumulants and baryon-strangeness correlations, comparing results with RHIC-BES II data, and finds no evidence of a critical point within the explored parameter range.

Contribution

It provides the first lattice QCD comparison of higher-order cumulant ratios and baryon-strangeness correlations with experimental data across a range of energies, constraining the QCD critical point.

Findings

No sign of a critical point within the explored parameter range.

Breakdown of HRG model at baryon chemical potentials above 1.

Good agreement with STAR and ALICE data at high energies.

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, $R_{12}^B$, agrees well with corresponding net-proton number cumulants down to $\sqrt{s_{NN}}=11.5$ GeV or baryon chemical potentials $\mu_B/T \le 2$. Likewise higher-order cumulant ratios, $R_{31}^B$ and $R_{42}^B$, 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 $\mu_B/T > 1$. 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.