Strangeness-correlations on the pseudocritical line in ( 2+1 )-flavor QCD

We present some lattice QCD results on first (χ1i) and second (χ2i) cumulants of and correlations (χ11ij) among net baryon-number (B), strangeness (S) and electric charge (Q) along the pseudocritical line Tpc (μB) in the temperature (T) –baryon chemical potential (μB) phase diagram of (2+1) -flavor QCD. We point out that violations of sum rules among second order cumulants, which hold in the isospin symmetric limit of vanishing electric charge chemical potential, are small along the Tpc (μB) for the entire range of μB covered in the RHIC beam energy scan. For the strangeness neutral matter produced in heavy-ion collisions this leads to a close relation between χ11BS and χ11QS. We compare lattice QCD results for χ11BS/χ2S along the Tpc (μB) line with preliminary experimental measurements of χ11BS/χ2S for collision energies 7. 7 GeV≤sNN≤62. 4 GeV. While we find good agreements for sNN≥39 GeV, differences are sizeable at smaller values of sNN. Moreover, we compare lattice QCD results for the ratio of the strangeness (μS) to baryon (μB) chemical potentials, which define a strangeness neutral system with fixed electric charge to baryon number density, with experimental results obtained by the STAR collaboration for μS/μB using strange baryon yields on the freeze-out line. Finally, we determine the baryon chemical potential at the freeze-out (μBf) by comparing χ1B/χ2B along the Tpc (μB) with the experimentally measured net-proton cumulants χ1p/χ2p. We find that μBf, Tpc (μBf) are consistent with the freeze-out parameters of the statistical-model fits to experimentally measured hadron yields for sNN≥11. 5 GeV. Published by the American Physical Society 2024