Abstract
We present new results on up to $6^{th}$ order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, $\mu_B$, obtained in lattice QCD calculations with physical values of light and strange quark masses. Representation of the Taylor expansions of higher order cumulants in terms of the ratio of the two lowest order cumulants, $M_B/\sigma_B^2=\chi_1^B(T,\mu_B)/\chi_2^B(T,\mu_B)$, allows for a parameter free comparison with data on net proton-number cumulants obtained by the STAR Collaboration in the Beam Energy Scan at RHIC. We show that recent high statistics data on skewness and kurtosis ratios of net proton-number distributions, obtained at beam energy $\sqrt{s_{_{NN}}}=54.4$ GeV, agree well with lattice QCD results on cumulants of net baryon-number fluctuations close to the pseudo-critical temperature, $T_{pc}(\mu_B)$, for the chiral transition in QCD. We also present first results from a next-to-leading order expansion of $5^{th}$ and $6^{th}$ order cumulants on the line of pseudo-critical temperatures.
Highlights
The phase diagram of strong-interaction matter at nonzero temperature and nonzero baryon-number density is being explored intensively through numerical calculations performed in the framework of lattice-regularized quantum chromodynamics (QCD) [1], as well as through ultrarelativistic heavy-ion collisions with varying beam energies [2]
We present new results on up to sixth-order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, μB, obtained in lattice QCD calculations with physical values of light and strange quark masses
We have presented new results on the μB dependence of up to sixth-order cumulants using our latest results on up to eighth-order cumulants calculated at vanishing chemical potentials
Summary
The phase diagram of strong-interaction matter at nonzero temperature and nonzero baryon-number density is being explored intensively through numerical calculations performed in the framework of lattice-regularized quantum chromodynamics (QCD) [1], as well as through ultrarelativistic heavy-ion collisions with varying beam energies [2]. Results, obtained with BES-I at RHIC, indicate that qualitative changes fluctuations occur in at thbeeabmehaevnioerrgoiefsnept pffisffiffirNffioffiNffiffito∼n-2n0umGbeeVr [17,18] This may hint at the existence of a critical point for large values of the baryon chemical potential. [19] at least for small values of the baryon chemical potential the first four cumulants of net baryon-number fluctuations, i.e., mean [MB ≡ χB1 ðT; μ⃗ Þ], variance [σ2B 1⁄4 χB2 ðT; μ⃗ Þ], skewness [SB 1⁄4 χB3 ðT; μ⃗ Þ= χB2 ðT; μ⃗ Þ3=2] and kurtosis [κB 1⁄4 χB4 ðT; μ⃗ Þ= χB2 ðT; μ⃗ Þ2] are predicted in QCD equilibrium thermodynamics to be related This relation, which is only slightly violated in strangeness neutral systems, has been established in lattice QCD calculations using next-to-leading-order (NLO) Taylor expansions of the first four cumulants of net baryon-number fluctuations [19].
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