Net-baryon-, net-proton-, and net-charge kurtosis in heavy-ion collisions within a relativistic transport approach

TL;DR

This study investigates net-baryon, net-proton, and net-charge kurtosis in heavy-ion collisions using a relativistic transport model, emphasizing charge conservation effects and providing baseline energy-dependent predictions.

Contribution

It introduces a method to account for exact charge conservation in kurtosis calculations and offers baseline predictions across a wide energy range.

Findings

Net-charge kurtosis remains around zero across energies.

Net-baryon kurtosis becomes significantly negative at lower energies.

Net-proton kurtosis is slightly negative at low collision energies.

Abstract

We explore the potential of net-baryon, net-proton and net-charge kurtosis measurements to investigate the properties of hot and dense matter created in relativistic heavy-ion collisions. Contrary to calculations in a grand canonical ensemble we explicitly take into account exact electric and baryon charge conservation on an event-by-event basis. This drastically limits the width of baryon fluctuations. A simple model to account for this is to assume a grand-canonical distribution with a sharp cut-off at the tails. We present baseline predictions of the energy dependence of the net-baryon, net-proton and net-charge kurtosis for central ($b\leq 2.75$ fm) Pb+Pb/Au+Au collisions from $E_{lab}=2A$ GeV to $\sqrt{s_{NN}}=200$ GeV from the UrQMD model. While the net-charge kurtosis is compatible with values around zero, the net-baryon number decreases to large negative values with decreasing beam energy. The net-proton kurtosis becomes only slightly negative for low $\sqrt{s_{NN}}$.