Extracting the strangeness freeze-out temperature from net-Kaon data at RHIC

Abstract

Using the moments of the net-kaon distribution calculated within a state of-the-art hadron resonance gas model compared to experimental data from STAR's Beam Energy Scan, we find that the extracted strange freeze-out temperature is incompatible with the light one extracted from net-proton and net-charge fluctuations. Additionally predictions for net-$Lambda$ fluctuations are made that also appear to be consistent with a higher freeze-out temperature for strange particles. This strangeness freeze-out temperature is roughly $10-15$ MeV higher than the corresponding light freeze-out temperature. We also discuss cross-susceptibilities using different identified particles, which may be a further test of this two freeze-out temperature picture. Finally, we lay out the necessary updates needed in relativistic hydrodynamic models to take into account for this two freeze-out temperature scenario and present preliminary results of $\Lambda$ spectra at RHIC for AuAu $\sqrt{s_{NN}}=200$ GeV collisions that indicate a higher freeze-out temperature is preferred.