Higher Moments of Net-Kaon Multiplicity Distributions at STAR

Abstract

Fluctuations of conserved quantities such as baryon number (B), electric charge number (Q), and strangeness number (S), are sensitive to the correlation length and can be used to probe non-gaussian fluctuations near the critical point. Experimentally, higher moments of the multiplicity distributions have been used to search for the QCD critical point in heavy-ion collisions. In this paper, we report the efficiency-corrected cumulants and their ratios of midrapidity (|y| < 0.5) net-kaon multiplicity distributions in Au+Au collisions at √ at RHIC. The centrality and energy dependence of the cumulants and their ratios, are presented. Furthermore, the comparisons with baseline calculations (Poisson) and non-critical-point models (UrQMD) are also discussed.

Lattice QCD and heavy ion collisions: a review of recent progress

“…Measuring the full strangeness fluctuations exper imentally represents unfortunately a remarkable challenge, since it would require the measurements of event-by-event distributions of rare states such as the multi-strange hadrons. Nevertheless, Kaon fluctuations have been presented by the STAR collaboration [138], and even Λ fluctuations might become available in the near future. Since the lattice QCD results are usually obtained for conserved charge fluctuations, while the identification of single particle contributions can be challenging, the authors of [103] have proposed a way to isolate kaon fluctuations from lattice QCD simulations.…”

“…CC BY 4.0. Right: χ 2 /χ 1 for charged Kaons: comparison between the preliminary STAR measurement at √ s = 200 GeV (orange band) [138] and the lattice QCD results (gray band). Reproduced with permission from [103].…”

Cumulants of event-by-event net-strangeness distributions in Au + Au collisions at sNN=7.7–200 GeV within an UrQMD model

“…Experimentally, the STAR experiment has reported the cumulants of net-kaon (proxy for net-strangeness) multiplicity distributions at √ s NN =7. 7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV [31,47]. However, the net-kaon is not a conserved quantity in QCD.…”

“…Thus, the yield ratios and fluctuations of strange particles have been studied at different experiments [32][33][34][35]. Experimentally, the STAR experiment has reported the cumulants of net-kaon (proxy for net-strangeness) multiplicity distributions at √ s NN =7.7, 11.5, 14.5, 19.6,27,39,62.4 and 200 GeV [31,47]. However, the net-kaon is not a conserved quantity in QCD.…”

Charge Conservation and Higher Moments of Charge Fluctuations

“…The measure is increasingly sensitive to the tails of the multiplicity distribution, P n , as n increases. The free energy, F ∼ a 2 (n − n) 2 + a 3 (n − n) 3 • • • , is minimized for n = n, but the quadratic part vanishes at the critical point, a 2 → 0, which allows the fluctuations to grow and be dominated by higher-order terms.…”