Strangeness-Correlations on the pseudo-critical 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 pseudo-critical line (Tpc(μB)) in the temperature (T)--baryon chemical potential (μB) phase diagram of (2+1)-flavor QCD. We point out that violations of 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≤ √s_NN≤ 62.4~ GeV. While we find good agreements for √s_NN≥ 39~GeV, differences are sizeable at smaller values of √s_NN. 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 √s_NN ≥ 11.5 GeV.