Beam energy dependence of net-$\Lambda$ fluctuations measured by the STAR experiment at RHIC

Abstract

The measurements of particle multiplicity distributions have generated considerable interest in understanding the fluctuations of conserved quantum numbers in the Quantum Chromodynamics (QCD) hadronization regime, in particular near a possible critical point and near the chemical freeze-out. We report the measurement of efficiency and centrality bin width corrected cumulant ratios ($C_2/C_1$, $C_3/C_2$) of net-$\Lambda$ distributions, in the context of both strangeness and baryon number conservation, as a function of collision energy, centrality and rapidity. The results are for Au + Au collisions at five beam energies ($\sqrt{s_{NN}}$ = 19.6, 27, 39, 62.4 and 200 GeV) recorded with the Solenoidal Tracker at RHIC (STAR). We compare our results to the Poisson and negative binomial (NBD) expectations, as well as to Ultra-relativistic Quantum Molecular Dynamics (UrQMD) and Hadron Resonance Gas (HRG) model predictions. Both NBD and Poisson baselines agree with data within the statistical and systematic uncertainties. The ratios of the measured cumulants show no features of critical fluctuations. The chemical freeze-out temperatures extracted from a recent HRG calculation, which was successfully used to describe the net-proton, net-kaon and net-charge data, indicate $\Lambda$ freeze-out conditions similar to those of kaons. However, large deviations are found when comparing to temperatures obtained from net-proton fluctuations. The net-$\Lambda$ cumulants show a weak, but finite, dependence on the rapidity coverage in the acceptance of the detector, which can be attributed to quantum number conservation.

12 pages, 9 figures, 3 tables, submitted to Phys.Rev.C

References in corpus (9)

• The order of the quantum chromodynamics transition predicted by the standard model of particle physics
• Glauber Modeling in High Energy Nuclear Collisions
• Probing freeze-out conditions in heavy ion collisions with moments of charge fluctuations
• Scale for the Phase Diagram of Quantum Chromodynamics
• Freeze-out Conditions in Heavy Ion Collisions from QCD Thermodynamics
• QCD at finite chemical potential with six time slices
• Canonical partition function and finite density phase transition in lattice QCD
• Freeze-out conditions from net-proton and net-charge fluctuations at RHIC
• Off-diagonal correlators of conserved charges from lattice QCD and how to relate them to experiment

Cited by in corpus (11)

• Theoretical and Experimental Constraints for the Equation of State of Dense and Hot Matter
• Search for the QCD Critical Point in High Energy Nuclear Collisions
• Particlization of an interacting hadron resonance gas with global conservation laws for event-by-event fluctuations in heavy-ion collisions
• Constraining baryon annihilation in the hadronic phase of heavy-ion collisions via event-by-event fluctuations
• Collision energy dependence of the critical end point from baryon number fluctuations in the Linear Sigma Model with quarks
• Effects of centrality fluctuation and deuteron formation on proton number cumulant in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV from JAM model
• The sixth order cumulant of net-proton number in Binomial distribution at $\sqrt{s_{NN}}=$ 200 GeV
• Purity correction for cumulants of hyperon number distribution
• Generalized nonlinear Langevin equation from quantum nonlinear projection operator
• Beam Energy Dependence of Fifth and Sixth-Order Net-proton Number Fluctuations in Au+Au Collisions at RHIC
• Cumulants of net-strangeness multiplicity distributions at energies available at the BNL Relativistic Heavy Ion Collider